Compositions and methods for stimulating ventilatory and/or respiratory drive

ABSTRACT

A method of stimulating ventilatory and/or respiratory drive in a subject in need thereof includes administering to the subject a therapeutically effective amount of a composition comprising a cystine ester or a pharmaceutically acceptable salt thereof. Embodiments described herein relate to compositions and methods of stimulating ventilatory and/or respiratory drive in a subject in need thereof, and particularly relates to compositions and methods of treating breathing diseases and/or disorders associated with paired ventilatory and/or respiratory drive.

RELATED APPLICATION

This application claims priority from U.S. Provisional Application No.62/102,902, filed Jan. 13, 2015, the subject matter of which isincorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments described herein relate to compositions and methods ofstimulating ventilatory and/or respiratory drive in a subject in needthereof, and particularly relates to compositions and methods oftreating breathing diseases and/or disorders associated with impairedventilatory and/or respiratory drive.

BACKGROUND

Normal control of breathing is a complex process that involves thebody's interpretation and response to chemical stimuli, such as carbondioxide, pH and oxygen levels in blood, tissues and the brain. Breathingcontrol is also affected by wakefulness (i.e., whether the patient isawake or sleeping). Within the brain medulla there are respiratorycontrol centers that interpret the various signals that affectrespiration and issue commands to muscles that perform the work ofbreathing. Key muscle groups are located in the abdomen, diaphragm,larynx, pharynx and thorax. Sensors located centrally and peripherallyprovide input to the brain's central respiration control areas thatenable response to changing oxygen requirements.

Normal respiratory rhythm is maintained primarily by the body's rapidresponse to changes in carbon dioxide levels (CO₂). Increased CO₂ levelssignal the body to increase breathing rate and depth resulting in higheroxygen levels and subsequent lower CO₂ levels. Conversely, low CO₂levels can result in periods of apnea (no breathing) since thestimulation to breathe is absent. This is what happens when a personhyperventilates. Additionally, low blood oxygen levels stimulaterespiratory drive, and this mechanism can become the primary driver inpatients with chronically high PCO₂ levels.

Impaired ventilatory drive can complicate a broad spectrum of diseasesin pulmonary, sleep, and critical care medicine. Patients with variousforms of chronic obstructive pulmonary disease (COPD)—among which can beconsidered late-stage cystic fibrosis (CF)—can have impaired ventilatoryresponses when treated with oxygen or narcotics. In obstructive sleepapnea (OSA), intermittent hypoxia associated with impaired short- andlong-term facilitation of hypoxic ventilatory drive and with loop gainmay predispose to perioperative complications and adverse neurocognitivesequelae. A variety of other conditions with components of disorderedventilatory control—ranging from congestive heart failure (CHF) toArnold-Chiari malformation—can only be managed with mechanicalventilation. Additionally, endotracheally-intubated patients in thecritical care setting who require narcotics for pain control can becomeunmanageable if narcotic use is stopped, but can fail extubation becauseof respiratory depression if the narcotic is continued. These pulmonaryand critical care issues can be all the more challenging in patientswith underlying COPD, CF, CHF, OSA and other conditions affectingventilatory drive.

Few medications are effective as respiratory stimulants. Methylxanthinescan be effective in patients with apnea of prematurity, but are oftenineffective in older patients. Almitrine can transiently improveventilatory drive in adults with COPD. However, the administration ofalmitrine is associated with the development of pulmonary arterialhypertension and peripheral neuropathy; and it does not affect outcome.

Conditions associated with impaired ventilatory drive are common andhave a substantial public health impact. For example, large,population-based studies report a prevalence of moderate-severeobstructive sleep apnea of 2-14% of the American population—depending onage and gender—and prevalence may be higher (up to 38% of men) inpulmonary clinic. A significant proportion of patients with OSA haveimpaired ventilatory drive, particularly those who also have heartfailure. There is a large, unmet need for a safe and effectiverespiratory stimulant in pulmonary and critical care medicine.

Additionally, commonly used narcotic and benzodiazepine medicationssuppress ventilatory drive. Specifically, they depress the slope of therelationship between PCO₂ and minute ventilation. This is a major issuein several important settings. In the operating room and post-anesthesiacare setting, patients may have prolonged respiratory depressionassociated with pain control. This results in prolonged hospitalizationsor early, risky discharge and death. In the chronic pain population—inthe Veteran's Administration system, for example—death from nocturnalrespiratory depression is at epidemic proportions among patients onchronic opiate therapy. Opiate addiction is also at epidemic levels, andhundreds of young people die annually without an effective emergencyrespiratory stimulant. On the battlefield, medics can have to choosebetween excruciating pain and risk of death from respiratory depression.In the Intensive Care population, physicians often have to choosebetween the risk of being on the ventilator for one or more days and therisk of awaking a patient in pain and distress. This is a problem inpatients with a baseline blunted CO₂ response, such as patients withsevere COPD, CF or other obstructive lung disease. Emergency treatmentfor narcotic-induced respiratory depression is limited largely to theuse of narcotic antagonists, such as naloxone, which are effective atreversing the narcotic induced respiratory depression but also reversethe narcotic mediated pain control, exacerbating the original problem.Further, this treatment is specific to narcotics and is ineffective forbenzodiazepine or other sedative or anesthetic induced respiratorydepression. A respiratory stimulant that overcomes respiratorydepression from any source is needed to address these needs.

SUMMARY

Embodiments described herein relate to compositions and methods ofstimulating ventilatory and/or respiratory drive in a subject in needthereof, and particularly relates to compositions and methods oftreating breathing diseases and/or disorders associated with impairedventilatory and/or respiratory drive.

In some embodiments, the methods can include stimulating ventilatoryand/or respiratory drive in a subject in need thereof by administeringto the subject a therapeutically effective amount of a compositioncomprising a cystine ester or a pharmaceutically acceptable saltthereof. The therapeutically effective amount can be an amount effectiveto stimulate the ventilatory and/or respiratory drive of the subject,including increasing tidal volume and respiratory frequency. Thecomposition can be administered to the subject systemically by, forexample, topical (e.g., inhalation), enteral (e.g., oral), and/orparenteral (e.g., intravenous injection) administration.

In some embodiments, the cystine ester can have the formula:

where R¹ and R² are the same or different and are selected from thegroup consisting of H, unsubstituted or substituted C₁-C₂₄ alkyl, C₂-C₂₄alkenyl, C₂-C₂₄ alkynyl, C₃-C₂₀ aryl, heterocycloalkenyl containing from5-6 ring atoms, heteroaryl, and heterocyclyl containing from 5-14 ringatoms, and at least one of R¹ and R² is not a H; or pharmaceuticallyacceptable salts thereof.

In some embodiments, R¹ and R² are independently H or an unsubstitutedor substituted C₁-C₂₄ alkyl, and at least one of R¹ and R² is not a H.In other embodiments, R¹ and R² are independently selected from thegroup consisting of H, methyl, ethyl, propyl, and butyl, and at leastone of R¹ and R² is not a H.

In other embodiments, the cystine ester can be a cystine dialkyl ester,prodrug thereof, or pharmaceutically acceptable salt thereof. Thecystine dialkyl ester can be selected from the group consisting ofcystine dimethyl ester, cystine diethyl ester, combinations thereof, andpharmaceutically acceptable salts thereof.

In still other embodiments, the cystine dialkyl ester can be a D-cystinedialkyl ester or pharmaceutically acceptable salt thereof. For example,the D-cystine dialkyl ester can be a D-cystine dimethyl ester, D-cystinediethyl ester, or a pharmaceutically acceptable salt thereof.

In some embodiments, the subject can have or is at increased risk of abreathing disorder, such as respiratory depression, including narcotic,sedative, and/or anesthetic, induced respiratory drive or suppressesventilatory drive, sleep apnea (central, mixed and obstructive includingbut not limited to co-existing conditions of heart failure, kidneydisease and stroke), sleep-disordered breathing (especially with snoringand arousals), apnea of prematurity, allergies, neurological orneuromuscular diseases (e.g., stroke or amyotrophic lateral sclerosis(ALS)), weakened respiratory muscles, hypoventilation due to stroke,trauma, surgery and/or radiation, obesity-hypoventilation syndrome,primary alveolar hypoventilation syndrome, acquired centralhypoventilation syndromes (ACHS), congenital central hypoventilationsyndromes (CCHS), chronic bronchitis, Cheyne-Stokes respiration,dyspnea, altitude sickness or acclimatization to high altitude,hypopnea, hypoxia, hypercapnia, cystic fibrosis, chronic obstructivepulmonary disease (COPD), nasal septum deformation, tonsillitis,adenoiditis, and Arnold-Chiari syndrome; and the composition can beadministered to the subject to treat the breathing disorder. Forexample, the composition can be administered to the subject at an amounteffective to prevent the need for mechanical ventilation in subjectswith acutely impaired ventilatory and/or respiratory drive because of anacute exacerbation of an underlying lung disease or an acute requirementfor narcotic analgesia.

In other embodiments, the subject can have or has an increased risk ofrespiratory depression that is caused, for example, by an anesthetic, asleeping aid, a sedative, anxiolytic agent, a hypnotic agent, alcohol,and/or a narcotic.

In still other embodiments, the composition can be administered to asubject in combination with at least one additional therapeutic agentthat changes normal breathing in a subject. The additional agent can beselected from the group consisting of doxapram and enantiomers thereof,acetazolamide, almitrine, theophylline, caffeine, methylprogesterone andrelated compounds, sedatives that decrease arousal threshold in sleepdisordered breathing patients, sodium oxybate, benzodiazepine receptoragonists, orexin antagonists, tricyclic antidepressants, serotonergicmodulators, adenosine and adenosine receptor and nucleoside transportermodulators, cannabinoids, orexins, melatonin agonists, ampakines, andcombinations thereof.

In yet another embodiment, the composition and the agent are separatelyadministered to the subject. In yet another embodiment, the compound andthe agent are co-administered to the subject, further wherein thecomposition and the agent are physically mixed or physically separatedwhen administered to the subject.

In one embodiment, the subject is further administered at least oneadditional therapeutic agent that changes normal breathing control inthe subject. In another embodiment, the additional agent is at least oneselected from the group consisting of opioid narcotics, benzodiazepines,sedatives, sleeping aids, hypnotics, propofol, and any combinationsthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1(A-C) illustrate plots showing the ventilatory responses elicitedby vehicle (saline) and test compounds (500 μmol/kg, i.v.) in consciousrats. Each drug was given to a separate group of rats (n=8 per group).Data are presented as mean±SEM.

FIGS. 2(A-C) illustrate plots showing the total responses elicited bythe test compounds (500 μmol/kg, i.v.) in conscious rats. Each compoundwas given to a separate group of rats (n=8 rats per group). Data aremean±SEM. *P<0.05, significant response. ^(†)P<0.05, d-Cystine diMEversus other agents.

FIGS. 3(A-B) illustrate plots showing dose-dependent changes inventilatory parameters elicited by D-Cystine diME in conscious rats.Each dose was given to a separate group of rats (n=8 rats per group).The data are presented as mean±SEM.

FIGS. 4(A-B) illustrate plots showing ventilatory responses elicited byvehicle (saline) or D-Cystine diME (250 mol/kg, i.v.) in conscious mice.Each drug was given to a separate group of mice (n=8 mice per group).The data are presented as mean±SEM. *P<0.05, significant response.‡P<0.05, d-CYS diME versus other agents.

FIGS. 5(A-F) illustrate plots showing ventilatory responses includingtidal volume/inspiratory time (Vt/Ti) elicited by vehicle (saline) orD-Cystine diEE (500 μmol/kg, i.v.) in rats which had received a bolusdose of morphine (10 mg/kg, i.v.). There were 9 rats in each group. Dataare mean±SEM. *P<0.05, difference from pre-values. ^(†)P<0.05, D-Cystineor D-Cystine diME versus vehicle.

FIGS. 6(A-E) illustrate graphs showing the effects of D-Cystine (500μmol/kg, i.v.) and D-Cystine diME (500 μmol/kg, i.v.) on arterialblood-gas chemistry and A-a gradients in rats which had previouslyreceived a bolus injection of morphine (10 mg/kg, i.v.). Data aremean±SEM (n=9 rats per group). *P<0.05, difference from pre-values.^(†)P<0.05, D-Cystine or D-Cystine diME versus vehicle.

FIGS. 7(A-B) illustrate a plot and graph showing ventilatory responsesincluding tidal volume/inspiratory time (Vt/Ti) elicited by vehicle(saline) or D-CYSee (2×500 μmol/kg, i.v.) in rats which had received abolus dose of morphine (10 mg/kg, i.v.). There were 9 rats in eachgroup. Data are mean±SEM. *P<0.05, difference from pre-values.^(†)P<0.05, D-Cystine diME versus vehicle.

FIGS. 8(A-B) illustrate graphs showing the effects of D-Cysteine (500μmol/kg, i.v.) and D-CYSee (500 μmol/kg, i.v.) on arterial blood-gaschemistry and A-a gradients in rats which had received an injection ofmorphine (10 mg/kg, i.v.). Data are presented mean±SEM (n=9 rats pergroup). *P<0.05, difference from pre-values. ^(†)P<0.05, D-Cysteine orD-CYSee versus vehicle.

FIGS. 9(A-E) illustrate plots showing the effects of prior infusion ofL-CYSee (total dose of 500 μmol/kg, i.v.) on the ventilatory depressanteffects of morphine (10 mg/kg, i.v.) in conscious rats. Responseselicited by a bolus injection of L-CYSee (250 μmol/kg, i.v.) are alsoshown. Data are presented mean±SEM (n=9 rats per group).

FIGS. 10(A-B) illustrate graphs showing the effects of prior infusion ofL-SERee or L-CYSee (total dose of 500 μmol/kg, i.v.) on changes inarterial blood-gas chemistry and A-a gradient elicited by morphine (10mg/kg, i.v.) in conscious rats. Data are presented mean±SEM (n=9 ratsper group). *P<0.05, difference from pre-values. ^(†)P<0.05, L-SERee orL-CYSee versus vehicle.

FIGS. 11(A-C) illustrate plots showing the effects of test agents (500μmol/kg, i.v.) on hemodynamic variables. Data are presented mean±SEM(n=8 rats per group). D-Cystine diME did not elicit significantresponses (P>0.05 for all comparisons to Pre).

FIG. 12 illustrates a plot showing the effects of pretreatment withD-CYSee (500 μmol/kg, i.v.) on morphine-induced (5 mg/kg, i.v.)analgesia (paw withdrawal latency assay) in conscious rats. The data arepresented as mean±SEM (n=6 rats per group). *P<0.05, difference frompre-values. ^(†)P<0.05, D-CYSee versus vehicle.

FIG. 13 illustrates a plot showing the effects of D-cystine diME onmorphine induced analgesia.

DETAILED DESCRIPTION

For convenience, certain terms employed in the specification, examples,and appended claims are collected here. Unless defined otherwise, alltechnical and scientific terms used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which thisapplication belongs.

The articles “a” and “an” are used herein to refer to one or to morethan one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” means one element or more thanone element.

The terms “comprise,” “comprising,” “include,” “including,” “have,” and“having” are used in the inclusive, open sense, meaning that additionalelements may be included. The terms “such as”, “e.g.”, as used hereinare non-limiting and are for illustrative purposes only. “Including” and“including but not limited to” are used interchangeably.

The term “or” as used herein should be understood to mean “and/or”,unless the context clearly indicates otherwise.

The term “about” or “approximately” as used herein refers to a quantity,level, value, number, frequency, percentage, dimension, size, amount,weight or length that varies by as much as 15%, 10%, 9%, 8%, 7%, 6%, 5%,4%, 3%, 2% or 1% to a reference quantity, level, value, number,frequency, percentage, dimension, size, amount, weight or length. In oneembodiment, the term “about” or “approximately” refers a range ofquantity, level, value, number, frequency, percentage, dimension, size,amount, weight or length ±15%, ±10%, ±9%, ±8%, ±7%, ±6%, ±5%, ±4%, ±3%,±2%, or ±1% about a reference quantity, level, value, number, frequency,percentage, dimension, size, amount, weight or length.

It will be noted that the structure of some of the compounds of theapplication include asymmetric (chiral) carbon or sulfur atoms. It is tobe understood accordingly that the isomers arising from such asymmetryare included herein, unless indicated otherwise. Such isomers can beobtained in substantially pure form by classical separation techniquesand by stereochemically controlled synthesis. The compounds of thisapplication may exist in stereoisomeric form, therefore can be producedas individual stereoisomers or as mixtures.

The term “isomerism” refers to compounds that have identical molecularformulae but that differ in the nature or the sequence of bonding oftheir atoms or in the arrangement of their atoms in space. Isomers thatdiffer in the arrangement of their atoms in space are termed“stereoisomers”. Stereoisomers that are not mirror images of one anotherare termed “diastereoisomers”, and stereoisomers that arenon-superimposable mirror images are termed “enantiomers”, or sometimesoptical isomers. A carbon atom bonded to four nonidentical substituentsis termed a “chiral center” whereas a sulfur bound to three or fourdifferent substitutents, e.g., sulfoxides or sulfinimides, is likewisetermed a “chiral center”.

The term “chiral isomer” refers to a compound with at least one chiralcenter. It has two enantiomeric forms of opposite chirality and mayexist either as an individual enantiomer or as a mixture of enantiomers.A mixture containing equal amounts of individual enantiomeric forms ofopposite chirality is termed a “racemic mixture”. A compound that hasmore than one chiral center has 2n−1 enantiomeric pairs, where n is thenumber of chiral centers. Compounds with more than one chiral center mayexist as either an individual diastereomer or as a mixture ofdiastereomers, termed a “diastereomeric mixture”. When one chiral centeris present, a stereoisomer may be characterized by the absoluteconfiguration (R or S) of that chiral center. Alternatively, when one ormore chiral centers are present, a stereoisomer may be characterized as(+) or (−). Absolute configuration refers to the arrangement in space ofthe substituents attached to the chiral center. The substituentsattached to the chiral center under consideration are ranked inaccordance with the Sequence Rule of Cahn, Ingold and Prelog. (Cahn etal, Angew. Chem. Inter. Edit. 1966, 5, 385; errata 511; Cahn et al.,Angew. Chem. 1966, 78, 413; Cahn and Ingold, J Chem. Soc. 1951 (London),612; Cahn et al., Experientia 1956, 12, 81; Cahn, J., Chem. Educ. 1964,41, 116).

The term “geometric isomers” refers to diastereomers that owe theirexistence to hindered rotation about double bonds. These configurationsare differentiated in their names by the prefixes cis and trans, or Zand E, which indicate that the groups are on the same or opposite sideof the double bond in the molecule according to the Cahn-Ingold-Prelogrules. Further, the structures and other compounds discussed in thisapplication include all atropic isomers thereof.

The term “atropic isomers” refers to a type of stereoisomer in which theatoms of two isomers are arranged differently in space. Atropic isomersowe their existence to a restricted rotation caused by hindrance ofrotation of large groups about a central bond. Such atropic isomerstypically exist as a mixture, however as a result of recent advances inchromatography techniques, it has been possible to separate mixtures oftwo atropic isomers in select cases.

The term “apnea” refers to the absence of normal breathing resulting inintermittent stoppages of breathing.

The term “Cheyne-Stokes respiration” refers to a specific pattern ofbreathing characterized by a crescendo pattern of breathing that resultsin apneas and/or hypopneas. A hallmark of this condition is thatbreathing becomes out of phase with blood oxygen levels.

The term “patency” refers to the state or condition of an airway beingopen or unblocked.

The term “hypopnea” is similar in many respects to apnea; however,breathing does not fully stop but is partially stopped (i.e., less than100% of normal breathing, but more than 0% of normal breathing).Hypopnea is also referred to herein as “partial apnea” and can besubdivided into obstructive, central or mixed types.

The term “hypoxia” refers to a deficiency in the amount of oxygen, beingtaken in by an organism, as well as to a deficiency in the amount ofoxygen, which is transported to tissues in an organism.

The term “normoxia” refers to a homoeostasis or “normal condition”regarding the amount of oxygen being taken in by an organism, as well asto a homeostasis or “normal condition” with respect to the amount ofoxygen which is transported to tissues in an organism.

The phrases “parenteral administration” and “administered parenterally”are art-recognized terms, and include modes of administration other thanenteral and topical administration, such as injections, and include,without limitation, intravenous, intramuscular, intrapleural,intravascular, intrapericardial, intraarterial, intrathecal,intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal,transtracheal, subcutaneous, subcuticular, intra-articular, subcapsular,subarachnoid, intraspinal and intrastemal injection and infusion.

The term “treating” is art-recognized and includes inhibiting a disease,disorder or condition in a subject, e.g., impeding its progress; andrelieving the disease, disorder or condition, e.g., causing regressionof the disease, disorder and/or condition. Treating the disease orcondition includes ameliorating at least one symptom of the particulardisease or condition, even if the underlying pathophysiology is notaffected.

The term “preventing” is art-recognized and includes stopping a disease,disorder or condition from occurring in a subject, which may bepredisposed to the disease, disorder and/or condition but has not yetbeen diagnosed as having it. Preventing a condition related to a diseaseincludes stopping the condition from occurring after the disease hasbeen diagnosed but before the condition has been diagnosed.

The term “pharmaceutical composition” refers to a formulation containingthe disclosed compounds in a form suitable for administration to asubject. In some embodiments, the pharmaceutical composition is in bulkor in unit dosage form. The unit dosage form is any of a variety offorms, including, for example, a capsule, an IV bag, a tablet, a singlepump on an aerosol inhaler, or a vial. The quantity of active ingredient(e.g., a formulation of the disclosed compound or salts thereof) in aunit dose of composition is an effective amount and is varied accordingto the particular treatment involved. One skilled in the art willappreciate that it is sometimes necessary to make routine variations tothe dosage depending on the age and condition of the patient. The dosagewill also depend on the route of administration. A variety of routes arecontemplated, including oral, pulmonary, rectal, parenteral,transdermal, subcutaneous, intravenous, intramuscular, intraperitoneal,intranasal, inhalational, and the like. Dosage forms for the topical ortransdermal administration of a compound described herein includespowders, sprays, ointments, pastes, creams, lotions, gels, solutions,patches, nebulized compounds, and inhalants. In some embodiments, thecompound or active ingredient is mixed under sterile conditions with apharmaceutically acceptable carrier, and with any preservatives,buffers, or propellants that are required.

The term “flash dose” refers to compound formulations that are rapidlydispersing dosage forms.

The term “immediate release” is defined as a release of compound from adosage form in a relatively brief period of time, generally up to about60 minutes. The term “modified release” is defined to include delayedrelease, extended release, and pulsed release. The term “pulsed release”is defined as a series of releases of drug from a dosage form. The term“sustained release” or “extended release” is defined as continuousrelease of a compound from a dosage form over a prolonged period.

The phrase “pharmaceutically acceptable” is art-recognized. In certainembodiments, the term includes compositions, polymers and othermaterials and/or dosage forms which are, within the scope of soundmedical judgment, suitable for use in contact with the tissues of humanbeings and animals without excessive toxicity, irritation, allergicresponse, or other problem or complication, commensurate with areasonable benefit/risk ratio.

The phrase “pharmaceutically acceptable carrier” is art-recognized, andincludes, for example, pharmaceutically acceptable materials,compositions or vehicles, such as a liquid or solid filler, diluent,excipient, solvent or encapsulating material, involved in carrying ortransporting any subject composition from one organ, or portion of thebody, to another organ, or portion of the body. Each carrier must be“acceptable” in the sense of being compatible with the other ingredientsof a subject composition and not injurious to the patient. In certainembodiments, a pharmaceutically acceptable carrier is non-pyrogenic.Some examples of materials, which may serve as pharmaceuticallyacceptable carriers include: (1) sugars, such as lactose, glucose andsucrose; (2) starches, such as corn starch and potato starch; (3)cellulose, and its derivatives, such as sodium carboxymethyl cellulose,ethyl cellulose and cellulose acetate; (4) powdered tragacanth; (5)malt; (6) gelatin; (7) talc; (8) excipients, such as cocoa butter andsuppository waxes; (9) oils, such as peanut oil, cottonseed oil,sunflower oil, sesame oil, olive oil, corn oil and soybean oil; (10)glycols, such as propylene glycol; (11) polyols, such as glycerin,sorbitol, mannitol and polyethylene glycol; (12) esters, such as ethyloleate and ethyl laurate; (13) agar; (14) buffering agents, such asmagnesium hydroxide and aluminum hydroxide; (15) alginic acid; (16)pyrogen-free water; (17) isotonic saline; (18) Ringer's solution; (19)ethyl alcohol; (20) phosphate buffer solutions; and (21) other non-toxiccompatible substances employed in pharmaceutical formulations.

The compounds of the application are capable of further forming salts.All of these forms are also contemplated herein.

“Pharmaceutically acceptable salt” of a compound means a salt that ispharmaceutically acceptable and that possesses the desiredpharmacological activity of the parent compound. For example, the saltcan be an acid addition salt. One embodiment of an acid addition salt isa hydrochloride salt. The pharmaceutically acceptable salts can besynthesized from a parent compound that contains a basic or acidicmoiety by conventional chemical methods. Generally, such salts can beprepared by reacting the free acid or base forms of these compounds witha stoichiometric amount of the appropriate base or acid in water or inan organic solvent, or in a mixture of the two; generally, non-aqueousmedia like ether, ethyl acetate, ethanol, isopropanol, or acetonitrilebeing preferred. Lists of salts are found in Remington's PharmaceuticalSciences, 18th ed. (Mack Publishing Company, 1990).

The compounds described herein can also be prepared as esters, forexample pharmaceutically acceptable esters. For example, a carboxylicacid function group in a compound can be converted to its correspondingester, e.g., a methyl, ethyl, or other ester. Also, an alcohol group ina compound can be converted to its corresponding ester, e.g., anacetate, propionate, or other ester.

The compounds described herein can also be prepared as prodrugs, forexample pharmaceutically acceptable prodrugs. The terms “pro-drug” and“prodrug” are used interchangeably herein and refer to any compound,which releases an active parent drug in vivo. Since prodrugs are knownto enhance numerous desirable qualities of pharmaceuticals (e.g.,solubility, bioavailability, manufacturing, etc.) the compounds can bedelivered in prodrug form. Thus, the compounds described herein areintended to cover prodrugs of the presently claimed compounds, methodsof delivering the same and compositions containing the same. “Prodrugs”are intended to include any covalently bonded carriers that release anactive parent drug in vivo when such prodrug is administered to asubject. Prodrugs are prepared by modifying functional groups present inthe compound in such a way that the modifications are cleaved, either inroutine manipulation or in vivo, to the parent compound. Prodrugsinclude compounds wherein a hydroxy, amino, sulfhydryl, carboxy, orcarbonyl group is bonded to any group that may be cleaved in vivo toform a free hydroxyl, free amino, free sulfhydryl, free carboxy or freecarbonyl group, respectively. Prodrugs can also include a precursor(forerunner) of a compound described herein that undergoes chemicalconversion by metabolic processes before becoming an active or moreactive pharmacological agent or active compound described herein.

Examples of prodrugs include, but are not limited to, esters (e.g.,acetate, dialkylaminoacetates, formates, phosphates, sulfates, andbenzoate derivatives) and carbamates (e.g., N,N-dimethylaminocarbonyl)of hydroxy functional groups, ester groups (e.g., ethyl esters,morpholinoethanol esters) of carboxyl functional groups, N-acylderivatives (e.g., N-acetyl) N-Mannich bases, Schiff bases andenaminones of amino functional groups, oximes, acetals, ketals and enolesters of ketone and aldehyde functional groups in compounds, and thelike, as well as sulfides that are oxidized to form sulfoxides orsulfones.

The term “protecting group” refers to a grouping of atoms that whenattached to a reactive group in a molecule masks, reduces or preventsthat reactivity. Examples of protecting groups can be found in Green andWuts, Protective Groups in Organic Chemistry, (Wiley, 2.sup.nd ed.1991); Harrison and Harrison et al., Compendium of Synthetic OrganicMethods, Vols. 1-8 (John Wiley and Sons, 1971-1996); and Kocienski,Protecting Groups, (Verlag, 3^(rd) ed. 2003).

The term “amine protecting group” is intended to mean a functional groupthat converts an amine, amide, or other nitrogen-containing moiety intoa different chemical group that is substantially inert to the conditionsof a particular chemical reaction. Amine protecting groups arepreferably removed easily and selectively in good yield under conditionsthat do not affect other functional groups of the molecule. Examples ofamine protecting groups include, but are not limited to, formyl, acetyl,benzyl, t-butyldimethylsilyl, t-butyldiphenylsilyl, t-butyloxycarbonyl(Boc), p-methoxybenzyl, methoxymethyl, tosyl, trifluoroacetyl,trimethylsilyl (TMS), fluorenyl-methyloxycarbonyl,2-trimethylsilyl-ethyoxycarbonyl, 1-methyl-1-(4-biphenylyl)ethoxycarbonyl, allyloxycarbonyl, benzyloxycarbonyl (CBZ),2-trimethylsilyl-ethanesulfonyl (SES), trityl and substituted tritylgroups, 9-fluorenylmethyloxycarbonyl (FMOC), nitro-veratryloxycarbonyl(NVOC), and the like. Those of skill in the art can identify othersuitable amine protecting groups.

Representative hydroxy protecting groups include those where the hydroxygroup is either acylated or alkylated such as benzyl, and trityl ethersas well as alkyl ethers, tetrahydropyranyl ethers, trialkylsilyl ethersand allyl ethers.

Additionally, the salts of the compounds described herein, can exist ineither hydrated or unhydrated (the anhydrous) form or as solvates withother solvent molecules. Nonlimiting examples of hydrates includemonohydrates, dihydrates, etc. Nonlimiting examples of solvates includeethanol solvates, acetone solvates, etc.

The term “solvates” means solvent addition forms that contain eitherstoichiometric or non stoichiometric amounts of solvent. Some compoundshave a tendency to trap a fixed molar ratio of solvent molecules in thecrystalline solid state, thus forming a solvate. If the solvent is waterthe solvate formed is a hydrate, when the solvent is alcohol, thesolvate formed is an alcoholate. Hydrates are formed by the combinationof one or more molecules of water with one of the substances in whichthe water retains its molecular state as H₂O, such combination beingable to form one or more hydrate.

The compounds, salts and prodrugs described herein can exist in severaltautomeric forms, including the enol and imine form, and the keto andenamine form and geometric isomers and mixtures thereof. Tautomers existas mixtures of a tautomeric set in solution. In solid form, usually onetautomer predominates. Even though one tautomer may be described, thepresent application includes all tautomers of the present compounds. Atautomer is one of two or more structural isomers that exist inequilibrium and are readily converted from one isomeric form to another.This reaction results in the formal migration of a hydrogen atomaccompanied by a switch of adjacent conjugated double bonds. Insolutions where tautomerization is possible, a chemical equilibrium ofthe tautomers will be reached. The exact ratio of the tautomers dependson several factors, including temperature, solvent, and pH. The conceptof tautomers that are interconvertable by tautomerizations is calledtautomerism.

Of the various types of tautomerism that are possible, two are commonlyobserved. In keto-enol tautomerism a simultaneous shift of electrons anda hydrogen atom occurs.

Tautomerizations can be catalyzed by: Base: 1. deprotonation; 2.formation of a delocalized anion (e.g., an enolate); 3. protonation at adifferent position of the anion; Acid: 1. protonation; 2. formation of adelocalized cation; 3. deprotonation at a different position adjacent tothe cation.

A “patient,” “subject,” or “host” to be treated by the compounds ormethods described herein may mean either a human or non-human animal,such as a mammal, a fish, a bird, a reptile, or an amphibian. Thus, thesubject of the herein disclosed methods can be a human, non-humanprimate, horse, pig, rabbit, dog, sheep, goat, cow, cat, guinea pig orrodent. The term does not denote a particular age or sex. Thus, adultand newborn subjects, as well as fetuses, whether male or female, areintended to be covered. In one aspect, the subject is a mammal. Apatient refers to a subject afflicted with a disease or disorder.

The terms “prophylactic” or “therapeutic” treatment is art-recognizedand includes administration to the host of one or more of the subjectcompounds. If it is administered prior to clinical manifestation of theunwanted condition (e.g., disease or other unwanted state of the hostanimal) then the treatment is prophylactic, i.e., it protects the hostagainst developing the unwanted condition, whereas if it is administeredafter manifestation of the unwanted condition, the treatment istherapeutic (i.e., it is intended to diminish, ameliorate, or stabilizethe existing unwanted condition or side effects thereof).

The terms “therapeutic agent”, “drug”, “medicament”, “activeingredient”, and “bioactive substance” are art-recognized and includemolecules and other agents that are biologically, physiologically, orpharmacologically active substances that act locally or systemically ina patient or subject to treat a disease or condition. The terms includewithout limitation pharmaceutically acceptable salts thereof andprodrugs. Such agents may be acidic, basic, or salts; they may beneutral molecules, polar molecules, or molecular complexes capable ofhydrogen bonding; they may be prodrugs in the form of ethers, esters,amides and the like that are biologically activated when administeredinto a patient or subject.

The phrase “therapeutically effective amount” or “pharmaceuticallyeffective amount” is an art-recognized term. In certain embodiments, theterm refers to an amount of a therapeutic agent that produces somedesired effect at a reasonable benefit/risk ratio applicable to anymedical treatment. In certain embodiments, the term refers to thatamount necessary or sufficient to eliminate, reduce or maintain a targetof a particular therapeutic regimen. The effective amount may varydepending on such factors as the disease or condition being treated, theparticular targeted constructs being administered, the size of thesubject or the severity of the disease or condition. One of ordinaryskill in the art may empirically determine the effective amount of aparticular compound without necessitating undue experimentation. Incertain embodiments, a therapeutically effective amount of a therapeuticagent for in vivo use will likely depend on a number of factors,including: the rate of release of an agent from a polymer matrix, whichwill depend in part on the chemical and physical characteristics of thepolymer; the identity of the agent; the mode and method ofadministration; and any other materials incorporated in the polymermatrix in addition to the agent.

With respect to any chemical compounds, the present application isintended to include all isotopes of atoms occurring in the presentcompounds. Isotopes include those atoms having the same atomic numberbut different mass numbers. By way of general example and withoutlimitation, isotopes of hydrogen include tritium and deuterium, andisotopes of carbon include C-13 and C-14.

When a bond to a substituent is shown to cross a bond connecting twoatoms in a ring, then such substituent can be bonded to any atom in thering. When a substituent is listed without indicating the atom via whichsuch substituent is bonded to the rest of the compound of a givenformula, then such substituent can be bonded via any atom in suchsubstituent. Combinations of substituents and/or variables arepermissible, but only if such combinations result in stable compounds.

When an atom or a chemical moiety is followed by a subscripted numericrange (e.g., C₁₋₆), it is meant to encompass each number within therange as well as all intermediate ranges. For example, “C₁₋₆ alkyl” ismeant to include alkyl groups with 1, 2, 3, 4, 5, 6, 1-6, 1-5, 1-4, 1-3,1-2, 2-6, 2-5, 2-4, 2-3, 3-6, 3-5, 3-4, 4-6, 4-5, and 5-6 carbons.

The term “alkyl” is intended to include both branched (e.g., isopropyl,tert-butyl, isobutyl), straight-chain e.g., methyl, ethyl, propyl,butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl), and cycloalkyl(e.g., alicyclic) groups (e.g., cyclopropyl, cyclopentyl, cyclohexyl,cycloheptyl, cyclooctyl), alkyl substituted cycloalkyl groups, andcycloalkyl substituted alkyl groups. Such aliphatic hydrocarbon groupshave a specified number of carbon atoms. For example, C₁₋₆ alkyl isintended to include C₁, C₂, C₃, C₄, C₅, and C₆ alkyl groups. As usedherein, “lower alkyl” refers to alkyl groups having from 1 to 6 carbonatoms in the backbone of the carbon chain. “Alkyl” further includesalkyl groups that have oxygen, nitrogen, sulfur or phosphorous atomsreplacing one or more hydrocarbon backbone carbon atoms. In certainembodiments, a straight chain or branched chain alkyl has six or fewercarbon atoms in its backbone (e.g., C₁-C₆ for straight chain, C₃-C₆ forbranched chain), for example four or fewer. Likewise, certaincycloalkyls have from three to eight carbon atoms in their ringstructure, such as five or six carbons in the ring structure.

The term “substituted alkyls” refers to alkyl moieties havingsubstituents replacing a hydrogen on one or more carbons of thehydrocarbon backbone. Such substituents can include, for example, alkyl,alkenyl, alkynyl, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl,arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl,dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate,phosphonato, phosphinato, cyano, amino (including alkylamino,dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino(including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido),amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromaticor heteroaromatic moiety. Cycloalkyls can be further substituted, e.g.,with the substituents described above. An “alkylaryl” or an “aralkyl”moiety is an alkyl substituted with an aryl (e.g., phenylmethyl(benzyl)). If not otherwise indicated, the terms “alkyl” and “loweralkyl” include linear, branched, cyclic, unsubstituted, substituted,and/or heteroatom-containing alkyl or lower alkyl, respectively.

The term “alkenyl” refers to a linear, branched or cyclic hydrocarbongroup of 2 to about 24 carbon atoms containing at least one double bond,such as ethenyl, n-propenyl, isopropenyl, n-butenyl, isobutenyl,octenyl, decenyl, tetradecenyl, hexadecenyl, eicosenyl, tetracosenyl,cyclopentenyl, cyclohexenyl, cyclooctenyl, and the like. Generally,although again not necessarily, alkenyl groups can contain 2 to about 18carbon atoms, and more particularly 2 to 12 carbon atoms. The term“lower alkenyl” refers to an alkenyl group of 2 to 6 carbon atoms, andthe specific term “cycloalkenyl” intends a cyclic alkenyl group,preferably having 5 to 8 carbon atoms. The term “substituted alkenyl”refers to alkenyl substituted with one or more substituent groups, andthe terms “heteroatom-containing alkenyl” and “heteroalkenyl” refer toalkenyl or heterocycloalkenyl (e.g., heterocylcohexenyl) in which atleast one carbon atom is replaced with a heteroatom. If not otherwiseindicated, the terms “alkenyl” and “lower alkenyl” include linear,branched, cyclic, unsubstituted, substituted, and/orheteroatom-containing alkenyl and lower alkenyl, respectively.

The term “alkynyl” refers to a linear or branched hydrocarbon group of 2to 24 carbon atoms containing at least one triple bond, such as ethynyl,n-propynyl, and the like. Generally, although again not necessarily,alkynyl groups can contain 2 to about 18 carbon atoms, and moreparticularly can contain 2 to 12 carbon atoms. The term “lower alkynyl”intends an alkynyl group of 2 to 6 carbon atoms. The term “substitutedalkynyl” refers to alkynyl substituted with one or more substituentgroups, and the terms “heteroatom-containing alkynyl” and“heteroalkynyl” refer to alkynyl in which at least one carbon atom isreplaced with a heteroatom. If not otherwise indicated, the terms“alkynyl” and “lower alkynyl” include linear, branched, unsubstituted,substituted, and/or heteroatom-containing alkynyl and lower alkynyl,respectively.

The terms “alkyl”, “alkenyl”, and “alkynyl” are intended to includemoieties which are diradicals, i.e., having two points of attachment. Anonlimiting example of such an alkyl moiety that is a diradical is—CH₂CH₂—, i.e., a C₂ alkyl group that is covalently bonded via eachterminal carbon atom to the remainder of the molecule.

The term “alkoxy” refers to an alkyl group bound through a single,terminal ether linkage; that is, an “alkoxy” group may be represented as—O-alkyl where alkyl is as defined above. A “lower alkoxy” group intendsan alkoxy group containing 1 to 6 carbon atoms, and includes, forexample, methoxy, ethoxy, n-propoxy, isopropoxy, t-butyloxy, etc.Preferred substituents identified as “C₁-C₆ alkoxy” or “lower alkoxy”herein contain 1 to 3 carbon atoms, and particularly preferred suchsubstituents contain 1 or 2 carbon atoms (i.e., methoxy and ethoxy).

The term “aryl” refers to an aromatic substituent containing a singlearomatic ring or multiple aromatic rings that are fused together,directly linked, or indirectly linked (such that the different aromaticrings are bound to a common group such as a methylene or ethylenemoiety). Aryl groups can contain 5 to 20 carbon atoms, and particularlypreferred aryl groups can contain 5 to 14 carbon atoms. Examples of arylgroups include benzene, phenyl, pyrrole, furan, thiophene, thiazole,isothiazole, imidazole, triazole, tetrazole, pyrazole, oxazole,isooxazole, pyridine, pyrazine, pyridazine, and pyrimidine, and thelike. Furthermore, the term “aryl” includes multicyclic aryl groups,e.g., tricyclic, bicyclic, e.g., naphthalene, benzoxazole,benzodioxazole, benzothiazole, benzoimidazole, benzothiophene,methylenedioxyphenyl, quinoline, isoquinoline, napthridine, indole,benzofuran, purine, benzofuran, deazapurine, or indolizine. Those arylgroups having heteroatoms in the ring structure may also be referred toas “aryl heterocycles”, “heterocycles,” “heteroaryls” or“heteroaromatics”. The aromatic ring can be substituted at one or morering positions with such substituents as described above, as forexample, halogen, hydroxyl, alkoxy, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl,alkylaminocarbonyl, aralkylaminocarbonyl, alkenylaminocarbonyl,alkylcarbonyl, arylcarbonyl, aralkylcarbonyl, alkenylcarbonyl,alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, phosphate,phosphonato, phosphinato, cyano, amino (including alkylamino,dialkylamino, arylamino, diaryl amino, and al kylaryl amino), acylamino(including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido),amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, alkylsulfinyl, sulfonato, sulfamoyl, sulfonamido, nitro,trifluoromethyl, cyano, azido, heterocyclyl, alkylaryl, or an aromaticor heteroaromatic moiety. Aryl groups can also be fused or bridged withalicyclic or heterocyclic rings, which are not aromatic so as to form amulticyclic system (e.g., tetralin, methylenedioxyphenyl). If nototherwise indicated, the term “aryl” includes unsubstituted,substituted, and/or heteroatom-containing aromatic substituents.

The terms “heterocyclyl” or “heterocyclic group” include closed ringstructures, e.g., 3- to 10-, or 4- to 7-membered rings, which includeone or more heteroatoms. “Heteroatom” includes atoms of any elementother than carbon or hydrogen. Examples of heteroatoms include nitrogen,oxygen, sulfur and phosphorus.

Heterocyclyl groups can be saturated or unsaturated and includepyrrolidine, oxolane, thiolane, piperidine, piperazine, morpholine,lactones, lactams, such as azetidinones and pyrrolidinones, sultams, andsultones. Heterocyclic groups such as pyrrole and furan can havearomatic character. They include fused ring structures, such asquinoline and isoquinoline. Other examples of heterocyclic groupsinclude pyridine and purine. The heterocyclic ring can be substituted atone or more positions with such substituents as described above, as forexample, halogen, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy,alkoxycarbonyloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl,alkoxycarbonyl, aminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate,phosphonato, phosphinato, cyano, amino (including alkyl amino,dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino(including alkylcarbonylamino, arylcarbonylamino, carbamoyl and ureido),amidino, imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate,sulfates, sulfonato, sulfamoyl, sulfonamido, nitro, trifluoromethyl,cyano, azido, heterocyclyl, or an aromatic or heteroaromatic moiety.Heterocyclic groups can also be substituted at one or more constituentatoms with, for example, a lower alkyl, a lower alkenyl, a lower alkoxy,a lower alkylthio, a lower alkylamino, a lower alkylcarboxyl, a nitro, ahydroxyl, —CF₃, or —CN, or the like.

The term “halo” or “halogen” refers to fluoro, chloro, bromo, and iodo.“Counterion” is used to represent a small, negatively charged speciessuch as fluoride, chloride, bromide, iodide, hydroxide, acetate, andsulfate. The term sulfoxide refers to a sulfur attached to 2 differentcarbon atoms and one oxygen and the S—O bond can be graphicallyrepresented with a double bond (S═O), a single bond without charges(S—O) or a single bond with charges [S(+)—O(−)].

The terms “substituted” as in “substituted alkyl,” “substituted aryl,”and the like, as alluded to in some of the aforementioned definitions,is meant that in the alkyl, aryl, or other moiety, at least one hydrogenatom bound to a carbon (or other) atom is replaced with one or morenon-hydrogen substituents. Examples of such substituents include,without limitation: functional groups such as halo, hydroxyl, silyl,sulfhydryl, C₁-C₂₄ alkoxy, C₂-C₂₄ alkenyloxy, C₂-C₂₄ alkynyloxy, C₅-C₂₀aryloxy, acyl (including C₂-C₂₄ alkylcarbonyl (—CO-alkyl) and C₆-C₂₀arylcarbonyl (—CO-aryl)), acyloxy (—O-acyl), C₂-C₂₄ alkoxycarbonyl(—(CO)—O-alkyl), C₆-C₂₀ aryloxycarbonyl (—(CO)—O-aryl), C₂-C₂₄alkylcarbonato (—O—(CO)—O-alkyl), C₆-C₂₀ arylcarbonato (—O—(CO)—O-aryl),carboxy (—COOH), carboxylato (—COO—), carbamoyl (—(CO)—NH₂),mono-(C₁-C₂₄ alkyl)-substituted carbamoyl (—(CO)—NH(C₁-C₂₄ alkyl)),di-(C₁-C₄ alkyl)-substituted carbamoyl (—(CO)—N(C₁-C₂₄ alkyl)₂),mono-substituted arylcarbamoyl (—(CO)—NH-aryl), thiocarbamoyl(—(CS)—NH₂), carbamido (—NH—(CO)—NH₂), cyano(—CN), isocyano (—N⁺C⁻),cyanato isocyanato (—ON⁺C⁻), isothiocyanato (—S—CN), azido (—N═N⁺═N⁻),formyl (—(CO)—H), thioformyl (—(CS)—H), amino (—NH₂), mono- anddi-(C₁-C₂₄ alkyl)-substituted amino, mono- and di-(C₅-C₂₀aryl)-substituted amino, C₂-C₂₄ alkylamido (—NH—(CO)-alkyl), C₆-C₂₀arylamido (—NH—(CO)-aryl), imino (—CR═NH where R=hydrogen, C₁-C₂₄ alkyl,C₅-C₂₀ aryl, C₆-C₂₄ alkaryl, C₆-C₂₄ aralkyl, etc.), alkylimino(—CR═N(alkyl), where R=hydrogen, alkyl, aryl, alkaryl, etc.), arylimino(—CR═N(aryl), where R=hydrogen, alkyl, aryl, alkaryl, etc.), nitro(—NO₂), nitroso (—NO), sulfo (—SO₂—OH), sulfonato (—SO₂—O⁻), C₁-C₂₄alkylsulfanyl (—S-alkyl; also termed “alkylthio”), arylsulfanyl(—S-aryl; also termed “arylthio”), C₁-C₂₄ alkylsulfinyl (—(SO)-alkyl),C₅-C₂₀ arylsulfinyl (—(SO)-aryl), C₁-C₂₄ alkylsulfonyl (—SO₂-alkyl),C₅-C₂₀ arylsulfonyl (—SO₂-aryl), phosphono (—P(O)(OH)₂), phosphonato(—P(O)(O⁻)₂), phosphinato (—P(O)(O⁻)), phospho (—PO₂), and phosphino(—PH₂); and the hydrocarbyl moieties C₁-C₂₄ alkyl, C₂-C₂₄ alkenyl,C₂-C₂₄ alkynyl, C₅-C₂₀ aryl, C₆-C₂₄ alkaryl, and C₆-C₂₄ aralkyl.

In addition, the aforementioned functional groups may, if a particulargroup permits, be further substituted with one or more additionalfunctional groups or with one or more hydrocarbyl moieties such as thosespecifically enumerated above. Analogously, the above-mentionedhydrocarbyl moieties may be further substituted with one or morefunctional groups or additional hydrocarbyl moieties such as thosespecifically enumerated.

When the term “substituted” appears prior to a list of possiblesubstituted groups, it is intended that the term apply to every memberof that group. For example, the phrase “substituted alkyl, alkenyl, andaryl” is to be interpreted as “substituted alkyl, substituted alkenyl,and substituted aryl.” Analogously, when the term“heteroatom-containing” appears prior to a list of possibleheteroatom-containing groups, it is intended that the term apply toevery member of that group. For example, the phrase“heteroatom-containing alkyl, alkenyl, and aryl” is to be interpreted as“heteroatom-containing alkyl, substituted alkenyl, and substituted aryl.

“Optional” or “optionally” means that the subsequently describedcircumstance may or may not occur, so that the description includesinstances where the circumstance occurs and instances where it does not.For example, the phrase “optionally substituted” means that anon-hydrogen substituent may or may not be present on a given atom, and,thus, the description includes structures wherein a non-hydrogensubstituent is present and structures wherein a non-hydrogen substituentis not present.

The terms “stable compound” and “stable structure” are meant to indicatea compound that is sufficiently robust to survive isolation, and asappropriate, purification from a reaction mixture, and formulation intoan efficacious therapeutic agent.

The terms “free compound” is used herein to describe a compound in theunbound state.

Throughout the description, where compositions are described as having,including, or comprising, specific components, it is contemplated thatcompositions also consist essentially of, or consist of, the recitedcomponents. Similarly, where methods or processes are described ashaving, including, or comprising specific process steps, the processesalso consist essentially of, or consist of, the recited processingsteps. Further, it should be understood that the order of steps or orderfor performing certain actions is immaterial so long as the compositionsand methods described herein remains operable. Moreover, two or moresteps or actions can be conducted simultaneously.

The term “small molecule” is an art-recognized term. In certainembodiments, this term refers to a molecule, which has a molecularweight of less than about 2000 amu, or less than about 1000 amu, andeven less than about 500 amu.

All percentages and ratios used herein, unless otherwise indicated, areby weight.

Embodiments described herein relate to compositions and methods ofstimulating ventilatory and/or respiratory drive in a subject in needthereof, and particularly relates to compositions methods of treatingbreathing diseases and/or disorders associated with impaired ventilatorand/or respiratory drive.

In some embodiments, the methods can include stimulating ventilatoryand/or respiratory drive in a subject in need thereof by administeringto the subject a therapeutically effective amount of a compositioncomprising a cystine ester, prodrugs thereof, or a pharmaceuticallyacceptable salt thereof.

It was found that cystine esters, such as cystine alkyl esters (e.g.,cystine dialkyl ester, cystine dimethyl ester or cystine diethyl ester)are potent stimulants of ventilatory and/or respiratory drive thateffectively overcome breathing disorders, such as narcotic inducedrespiratory depression. Advantageously, cystine esters described hereincan stimulate respiratory drive and overcome respiratorynarcotic-induced respiratory depression in a subject in need thereofwithout impairing, attenuating, and/or adversely affectingnarcotic-induced analgesia in the subject.

In some embodiments, the cystine esters described herein can beadministered to a subject in need thereof at an amount ortherapeutically effective amount to stimulate the ventilatory and/orrespiratory drive of the subject, including increasing tidal volume andrespiratory frequency, and treat breathing disorders in a subjectassociated with impaired ventilatory and/or respiratory drive.

In some embodiments, the cystine ester can have the formula:

where R¹ and R² are the same or different and are selected from thegroup consisting of H, unsubstituted or substituted C₁-C₂₄ alkyl, C₂-C₂₄alkenyl, C₂-C₂₄ alkynyl, C₃-C₂₀ aryl, heterocycloalkenyl containing from5-6 ring atoms (wherein from 1-3 of the ring atoms is independentlyselected from N, NH, N(C₁-C₆ alkyl), NC(O)(C₁-C₆ alkyl), O, and S),heteroaryl containing from 5-14 ring atoms, (wherein from 1-6 of thering atoms is independently selected from N, NH, N(C₁-C₃ alkyl), O, andS), and heterocyclyl containing from 5-14 ring atoms (wherein from 1-6of the ring atoms is independently selected from N, NH, N(C₁-C₃ alkyl),O, and S), and at least one of R¹ and R² is not a H; prodrugs thereof,or pharmaceutically acceptable salts thereof.

In some embodiments, R¹ and R² are independently H or an unsubstitutedor substituted C₁-C₂₄ alkyl, wherein at least one of R¹ and R² is not aH. In other embodiments, R¹ and R² are independently selected from thegroup consisting of H, methyl, ethyl, propyl, and butyl, and at leastone of R¹ and R² is not a H.

In other embodiments, the cystine ester can be a cystine dialkyl ester,prodrug thereof, or pharmaceutically acceptable salt thereof. Thecystine dialkyl ester can comprise a mixture at least one of D or Lisomers of a cystine dialkyl ester. For example, the cystine dialkylester can comprise a mixture of: less than about 50% by weight of the Disomer of a cystine dialkyl ester and greater than about 50% by weightof the L isomer of a cystine dialkyl ester, less than about 25% byweight of the D isomer of a cystine dialkyl ester and greater than about75% by weight of the L isomer of a cystine dialkyl ester, less thanabout 10% by weight of the D isomer of a cystine dialkyl ester andgreater than about 90% by weight of the L isomer of a cystine dialkylester, less than about 1% by weight of the D isomer of a cystine dialkylester and greater than about 99% by weight of the L isomer of a cystinedialkyl ester, greater than about 50% by weight of the D isomer of acystine dialkyl ester and less than about 50% by weight of the L isomerof a cystine dialkyl ester, greater than about 75% by weight of the Disomer of a cystine dialkyl ester and less than about 25% by weight ofthe L isomer of a cystine dialkyl ester, greater than about 90% byweight of the D isomer of a cystine dialkyl ester and less than about10% by weight of the L isomer of a cystine dialkyl ester, or greaterthan about 99% by weight of the D isomer of a cystine dialkyl ester andless than about 1% by weight of the L isomer of a cystine dialkyl ester.

In a still further embodiment, the cystine dialkyl ester can consistessentially of or consist of the D isomer of cystine dialkyl ester. Inyet another embodiment, the cystine dialkyl ester can consistessentially of or consist of the L isomer of cystine dialkyl ester.

In some embodiments, the cystine dialkyl ester is a D-cystine dialkylester, prodrug thereof, or pharmaceutically acceptable salt thereof.Advantageously, it was found that D-isomer can be more active than thecorresponding L-isomer of the cystine dialkyl ester and unlikeL-cysteine do not increase upper airway resistance or promotecystinosis-like effects in animals or have negative cardiovasculareffects of L-cysteine esters. The D-cystine dialkyl ester can beselected from the group consisting of D-cystine dimethyl ester,D-cystine diethyl ester, combinations thereof, prodrugs thereof, andpharmaceutically acceptable salts thereof.

Composition comprising the cystine esters described herein can beadministered to a subject to stimulate ventilatory and/or respiratorydrive in a subject in need thereof. In some embodiments, the subject canhave or is at increased risk of impaired ventilatory and/or respiratorydrive associated with a disorder or breathing disorder, such asrespiratory depression, including narcotic, sedative, and/or anesthetic,induced respiratory drive or suppresses ventilatory drive, sleep apnea(central, mixed and obstructive including but not limited to co-existingconditions of heart failure, kidney disease and stroke),sleep-disordered breathing (especially with snoring and arousals), apneaof prematurity, allergies, neurological or neuromuscular diseases (e.g.,stroke or amyotrophic lateral sclerosis (ALS)), weakened respiratorymuscles, hypoventilation due to stroke, trauma, surgery and/orradiation, obesity-hypoventilation syndrome, primary alveolarhypoventilation syndrome, acquired central hypoventilation syndromes(ACHS), congenital central hypoventilation syndromes (CCHS), chronicbronchitis, Cheyne-Stokes respiration, dyspnea, altitude sickness oracclimatization to high altitude, hypopnea, hypoxia, hypercapnia, cysticfibrosis, chronic obstructive pulmonary disease (COPD), nasal septumdeformation, tonsillitis, adenoiditis, and Arnold-Chiari syndrome. Thecomposition can be administered to the subject at an amount effective totreat and/or prevent the breathing disorder or impaired ventilatoryand/or respiratory drive associated with the disorder or breathingdisorder.

In some embodiments, the composition can be administered to the subjectto prevent the need for mechanical ventilation in subjects with acutelyimpaired ventilatory and/or respiratory drive because of an acuteexacerbation of an underlying lung disease or an acute requirement fornarcotic analgesia. For example, the subjects can be at-risk subjectswith severe, hypercapneic COPD or mixed apnea evident onpolysomnography.

In other embodiments, the subject can have or has an increased risk ofrespiratory depression or suppressed ventilatory drive that is caused,for example, by an anesthetic, a sedative, anxiolytic agent, a hypnoticagent, alcohol, and/or a narcotic. By way of a non-limiting example,narcotic analgesics (e.g., morphine, fentanyl, oxycodone, buprenorphine)are administered to cancer patients to alleviate pain. The dose is oftenlimited by a fear of respiratory depression. In addition, even a partialrespiratory depression from these drugs causes hypoxia and a resultingexcessive daytime sleepiness that can be debilitating and severelydecrease quality of life. General anesthetics can exert a similardepressant effect on respiration and delay a patient's transfer from theoperating room to a surgical recovery area. A composition comprising acystine ester described herein is therefore useful to counteract thelingering effects of the anesthetic, and for restoring adequaterespiratory drive to enable the patient to breathe on their own.

In other embodiments, a composition including the cystine ester can beadministered in ambulatory delivery formulations to treat respiratorydepression associated with narcotics, analgesics, sedatives, and/oropioids. The subject can be one who is taking and/or over-dosed on thenarcotics, analgesics, sedatives, and/or opioids and who is experiencingor at risk of acute respiratory depression. The compositions can beadministered to the subject to treat stimulate ventilatory and/orrespiratory drive and increase breathing frequency.

In some embodiments, compositions comprising the cystine estersdescribed herein can be administered to subject in combination with atleast one additional compound, agent, and/or therapeutic agent usefulfor treating the subject or the breathing disorder. These additionalcompounds, agents, and/or therapeutic agents can include commerciallyavailable agents or compounds, known to treat, prevent, or reduce thesymptoms of breathing disorders or treat the disorder in the subject.

In some embodiments, the at least one additional therapeutic agent canchange normal breathing in a subject. Such additional agents can beselected from the group consisting of doxapram and enantiomers thereof,acetazolamide, almitrine, theophylline, caffeine, methylprogesterone andrelated compounds, sedatives that decrease arousal threshold in sleepdisordered breathing patients, sodium oxybate, benzodiazepine receptoragonists, orexin antagonists, tricyclic antidepressants, serotonergicmodulators, adenosine and adenosine receptor and nucleoside transportermodulators, cannabinoids, orexins, melatonin agonists, ampakines, andcombinations thereof.

In other embodiments, compositions comprising the cystine estersdescribed herein and at least one additional compound has additive,complementary or synergistic effects in the treatment of the breathingdisorder or other disorder in the subject. In a non-limiting example,the compositions comprising the cystine esters described herein may beused concurrently or in combination with one or more of the followingdrugs: doxapram, enantiomers of doxapram, acetazolamide, almitrine,theophylline, caffeine, methylprogesterone and related compounds,sedatives that decrease arousal threshold in sleep disordered breathingpatients (such as eszopiclone and zolpidem), sodium oxybate,benzodiazepine receptor agonists (e.g., zolpidem, zaleplon, eszopiclone,estazolam, flurazepam, quazepam, temazepam, triazolam), orexinantagonists (e.g., suvorexant), tricyclic antidepressants (e.g.,doxepin), serotonergic modulators, adenosine and adenosine receptor andnucleoside transporter modulators, cannabinoids (such as, but notlimited to, dronabinol), orexins, melatonin agonists (such as ramelteon)and compounds known as ampakines.

Non-limiting examples of ampakines are the pyrrolidine derivativeracetam drugs such as piracetam and aniracetam; the “CX-” series ofdrugs which encompass a range of benzoylpiperidine andbenzoylpyrrolidine structures, such as CX-516(6-(piperidin-1-yl-carbonyl)quinoxaline), CX-546(2,3-dihydro-1,4-benzodioxin-7-yl-(1-piperidyl)-methanone), CX-614(2H,3H,6aH-pyrrolidino(2,1-3′,2′)-1,3-oxazino-(6′,5′-5,4)benzo(e)1,4-diox-an-10-one), CX-691 (2,1,3-benzoxadiazol-6-yl-piperidin-1-yl-methanone),CX-717, CX-701, CX-1739, CX-1763, and CX-1837; benzothiazidederivatives, such as cyclothiazide and IDRA-21(7-chloro-3-methyl-3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide);biarylpropylsulfonamides, such as LY-392,098, LY-404,187(N-[2-(4′-cyanobiphenyl-4-yl)propyl]propane-2-sulfonamide), LY-451,646and LY-503,430(4′-{(1S)-1-fluoro-2-[(isopropylsulfonyl)amino]-1-methylethyl}-N-methylbi-phenyl-4-carboxamide).

The combination of two or more compounds may refer to a compositionwherein the individual compounds are physically mixed or wherein theindividual compounds are physically separated. A combination therapyencompasses administering the components separately to produce thedesired additive, complementary or synergistic effects.

In one embodiment, the composition comprising the cystine estersdescribed herein and the agent are physically mixed in the composition.In another embodiment, the composition comprising the cystine estersdescribed herein and the agent are physically separated in thecomposition.

In one embodiment, compositions comprising the cystine esters describedherein are co-administered with a compound that is used to treat anotherdisorders but causes loss of breathing control. In this aspect,compositions comprising the cystine esters described herein block orotherwise reduce depressive effects on normal breathing control causedby the compound with which they are co-administered. Such compound thattreats another disorder but depresses breathing control includes but isnot limited to anesthetics, sedatives, sleeping aids, anxiolytics,hypnotics, alcohol, and narcotic analgesics. The co-administeredcompound may be administered individually, or a combined composition asa mixture of solids and/or liquids in a solid, gel or liquid formulationor as a solution, according to methods known to those familiar with theart.

In one embodiment, a composition comprising the cystine esters describedherein is co-administered with at least one additional compound usefulfor treating breathing control disorders and with at least one compoundthat is used to treat other disorder but causes a loss of breathingcontrol. In this aspect, the compound of the invention works in anadditive, complementary or synergistic manner with the co-administeredbreathing control agent to block or otherwise reduce depressive effectson normal breathing control caused by other compounds with which theyare combined. A synergistic effect may be calculated, for example, usingsuitable methods.

In some embodiments, a composition comprising the cystine estersdescribed herein may be packaged with at least one additional compounduseful for treating breathing control disorders. In another embodiment,a composition comprising the cystine esters described herein may bepackaged with a therapeutic agent known to cause changes in breathingcontrol, such as, but not limited to, anesthetics, sedatives,anxiolytics, hypnotics, alcohol, and narcotic analgesics. A co-packagemay be based upon, but not limited to, dosage units.

The cystine esters and/or additional compounds or agents describedherein can be provided in a pharmaceutical composition with apharmaceutically acceptable carrier or excipient. In some embodiment,pharmaceutical compositions that include the cystine esters describedherein may be formulated to deliver a dose to the subject of between 1ng/kg/day and 100 mg/kg/day. In another embodiment, the pharmaceuticalcompositions may be administered to deliver a dose of between 1ng/kg/day and 500 mg/kg/day.

The relative amounts of the cystine esters or active ingredient, thepharmaceutically acceptable carrier, and any additional ingredients in apharmaceutical composition can vary, depending upon the identity, size,and condition of the subject treated and further depending upon theroute by which the composition is to be administered. By way of example,the composition may comprise between 0.1% and 100% (w/w) activeingredient.

Pharmaceutical compositions that are useful in the methods describedherein may be suitably developed for nasal, inhalational, oral, rectal,vaginal, pleural, peritoneal, parenteral, topical, transdermal,pulmonary, intranasal, buccal, ophthalmic, epidural, intrathecal,intravenous or another route of administration. Other contemplatedformulations include projected nanoparticles, microspheres, liposomalpreparations, coated particles, and polymer conjugates.

In one embodiment, the compositions comprising the cystine estersdescribed herein are part of a pharmaceutical matrix, which allows formanipulation of insoluble materials and improvement of thebioavailability thereof, development of controlled or sustained releaseproducts, and generation of homogeneous compositions. By way of example,a pharmaceutical matrix may be prepared using hot melt extrusion, solidsolutions, solid dispersions, size reduction technologies, molecularcomplexes (e.g., cyclodextrins, and others), microparticulate, andparticle and formulation coating processes. Amorphous or crystallinephases may be used in such processes.

The route(s) of administration will be readily apparent to the skilledartisan and will depend upon any number of factors including the typeand severity of the disease being treated, the type and age of theveterinary or human patient being treated, and the like.

The formulations of the pharmaceutical compositions described herein maybe prepared by any method known or hereafter developed in the art ofpharmacology and pharmaceutics. In general, such preparatory methodsinclude the step of bringing the active ingredient into association witha carrier or one or more other accessory ingredients, and then, ifnecessary or desirable, shaping or packaging the product into a desiredsingle-dose or multi-dose unit.

As used herein, a “unit dose” is a discrete amount of the pharmaceuticalcomposition comprising a predetermined amount of the active ingredient.The amount of the active ingredient is generally equal to the dosage ofthe active ingredient that would be administered to a subject or aconvenient fraction of such a dosage such as, for example, one-half orone-third of such a dosage. The unit dosage form may be for a singledaily dose or one of multiple daily doses (e.g., about 1 to 4 or moretimes per day). When multiple daily doses are used, the unit dosage formmay be the same or different for each dose.

Although the descriptions of pharmaceutical compositions provided hereinare principally directed to pharmaceutical compositions, which aresuitable for ethical administration to humans, it will be understood bythe skilled artisan that such compositions are generally suitable foradministration to animals of all sorts. Modification of pharmaceuticalcompositions suitable for administration to humans in order to renderthe compositions suitable for administration to various animals is wellunderstood, and the ordinarily skilled veterinary pharmacologist candesign and perform such modification with merely ordinary, if any,experimentation. Subjects to which administration of the pharmaceuticalcompositions is contemplated include, but are not limited to, humans andother primates, mammals including commercially relevant mammals such ascattle, pigs, horses, sheep, cats, and dogs.

In one embodiment, the compositions described herein are formulatedusing one or more pharmaceutically acceptable excipients or carriersPharmaceutically acceptable carriers, which are useful, include, but arenot limited to, glycerol, water, saline, ethanol, recombinant humanalbumin, solubilized gelatins, and other pharmaceutically acceptablesalt solutions, such as phosphates and salts of organic acids. Examplesof these and other pharmaceutically acceptable carriers are described inRemington's Pharmaceutical Sciences (1991, Mack Publication Co., NewJersey).

In some embodiments, the carrier may be a solvent or dispersion mediumcontaining, for example, water, ethanol, polyol (for example, glycerol,propylene glycol, and liquid polyethylene glycol, and the like),recombinant human albumin, solubilized gelatins, suitable mixturesthereof, and vegetable oils. The proper fluidity may be maintained, forexample, by the use of a coating such as lecithin, by the maintenance ofthe required particle size in the case of dispersion and by the use ofsurfactants. Prevention of the action of microorganisms may be achievedby various antibacterial and antifungal agents, for example, parabens,chlorobutanol, phenol, ascorbic acid, thimerosal, and the like. In manycases, it will be preferable to include isotonic agents, for example,sugars, sodium chloride, or polyalcohols such as mannitol and sorbitol,in the composition. Prolonged absorption of the injectable compositionsmay be brought about by including in the composition an agent thatdelays absorption, for example, aluminum monostearate or gelatin.

Formulations of the compositions described herein may be employed inadmixtures with conventional excipients, i.e., pharmaceuticallyacceptable organic or inorganic carrier substances suitable for oral,parenteral, nasal, inhalational, intravenous, subcutaneous, transdermalenteral, or any other suitable mode of administration, known to the art.The pharmaceutical preparations may be sterilized and if desired mixedwith auxiliary agents, e.g., lubricants, preservatives, stabilizers,wetting agents, emulsifiers, salts for influencing osmotic pressurebuffers, coloring, flavoring and/or fragrance-conferring substances andthe like. They may also be combined where desired with other activeagents, e.g., other analgesic, anxiolytics or hypnotic agents. As usedherein, “additional ingredients” include, but are not limited to, one ormore ingredients that may be used as a pharmaceutical carrier.

The composition may comprise a preservative from about 0.005% to 2.0% bytotal weight of the composition. The preservative is used to preventspoilage in the case of exposure to contaminants in the environment.Examples of preservatives include but are not limited to those selectedfrom the group consisting of benzyl alcohol, sorbic acid, parabens,imidurea and combinations thereof. A particularly preservative is acombination of about 0.5% to 2.0% benzyl alcohol and 0.05% to 0.5%sorbic acid.

The composition can include an antioxidant and a chelating agent whichinhibit the degradation of the compound. Examples of antioxidants forsome compounds are BHT, BHA, alpha-tocopherol and ascorbic acid in therange of about 0.01% to 0.3% by weight by total weight of thecomposition. The chelating agent can be present in an amount of from0.01% to 0.5% by weight by total weight of the composition. Examples ofchelating agents include edetate salts (e.g., disodium edetate) andcitric acid in the weight range of about 0.01% to 0.20% by weight bytotal weight of the composition. The chelating agent is useful forchelating metal ions in the composition, which may be detrimental to theshelf life of the formulation.

Liquid suspensions may be prepared using conventional methods to achievesuspension of the active ingredient in an aqueous or oily vehicle.Aqueous vehicles include, for example, water, and isotonic saline. Oilyvehicles include, for example, almond oil, oily esters, ethyl alcohol,vegetable oils such as olive, sesame, or coconut oil, fractionatedvegetable oils, and mineral oils such as liquid paraffin. Liquidsuspensions may further comprise one or more additional ingredientsincluding, but not limited to, suspending agents, dispersing or wettingagents, emulsifying agents, demulcents, preservatives, buffers, salts,flavorings, coloring agents, and sweetening agents. Oily suspensions mayfurther comprise a thickening agent. Known suspending agents include,but are not limited to, sorbitol syrup, hydrogenated edible fats, sodiumalginate, polyvinylpyrrolidone, gum tragacanth, gum acacia, andcellulose derivatives such as sodium carboxymethylcellulose,methylcellulose, hydroxypropylmethylcellulose. Known dispersing orwetting agents include, but are not limited to, naturally-occurringphosphatides such as lecithin, condensation products of an alkyleneoxide with a fatty acid, with a long chain aliphatic alcohol, with apartial ester derived from a fatty acid and a hexitol, or with a partialester derived from a fatty acid and a hexitol anhydride (e.g.,polyoxyethylene stearate, heptadecaethyleneoxycetanol, polyoxyethylenesorbitol monooleate, and polyoxyethylene sorbitan monooleate,respectively). Known emulsifying agents include, but are not limited to,lecithin, acacia, and ionic or non ionic surfactants. Knownpreservatives include, but are not limited to, methyl, ethyl, orn-propyl para-hydroxybenzoates, ascorbic acid, and sorbic acid. Knownsweetening agents include, for example, glycerol, propylene glycol,sorbitol, sucrose, and saccharin.

Liquid solutions of the active ingredient in aqueous or oily solventsmay be prepared in substantially the same manner as liquid suspensions,the primary difference being that the active ingredient is dissolved,rather than suspended in the solvent. An “oily” liquid is one whichcomprises a carbon-containing liquid molecule and which exhibits a lesspolar character than water. Liquid solutions of the pharmaceuticalcomposition may comprise each of the components described with regard toliquid suspensions, it being understood that suspending agents will notnecessarily aid dissolution of the active ingredient in the solvent.Aqueous solvents include, for example, water, and isotonic saline. Oilysolvents include, for example, almond oil, oily esters, ethyl alcohol,vegetable oils such as arachis, olive, sesame, or coconut oil,fractionated vegetable oils, and mineral oils such as liquid paraffin.

Powdered and granular formulations of a pharmaceutical preparation maybe prepared using known methods. Such formulations may be administereddirectly to a subject, used, for example, to form tablets, to fillcapsules, or to prepare an aqueous or oily suspension or solution byaddition of an aqueous or oily vehicle thereto. Each of theseformulations may further comprise one or more of dispersing or wettingagent, a suspending agent, ionic and non-ionic surfactants, and apreservative. Additional excipients, such as fillers and sweetening,flavoring, or coloring agents, may also be included in theseformulations.

A pharmaceutical composition may also be prepared, packaged, or sold inthe form of oil-in-water emulsion or a water-in-oil emulsion. The oilyphase may be a vegetable oil, such as olive or arachis oil, a mineraloil, such as liquid paraffin, or a combination of these. Suchcompositions may further comprise one or more emulsifying agents such asnaturally occurring gums such as gum acacia or gum tragacanth,naturally-occurring phosphatides such as soybean or lecithinphosphatide, esters or partial esters derived from combinations of fattyacids and hexitol anhydrides such as sorbitan monooleate, andcondensation products of such partial esters with ethylene oxide such aspolyoxyethylene sorbitan monooleate. These emulsions may also containadditional ingredients including, for example, sweetening or flavoringagents.

Methods for impregnating or coating a material with a chemicalcomposition are known in the art, and include, but are not limited tomethods of depositing or binding a chemical composition onto a surface,methods of incorporating a chemical composition into the structure of amaterial during the synthesis of the material (i.e., such as with aphysiologically degradable material), and methods of absorbing anaqueous or oily solution or suspension into an absorbent material, withor without subsequent drying. Methods for mixing components includephysical milling, the use of pellets in solid and suspensionformulations and mixing in a transdermal patch, as known to thoseskilled in the art.

The regimen of administration may affect what constitutes an effectiveamount. The therapeutic formulations may be administered to the patienteither prior to or after the onset of a breathing disorder event.Further, several divided dosages, as well as staggered dosages may beadministered daily or sequentially, or the dose may be continuouslyinfused, or may be a bolus injection. Further, the dosages of thetherapeutic formulations may be proportionally increased or decreased asindicated by the exigencies of the therapeutic or prophylacticsituation.

Administration of the compositions described herein to a patient,preferably a mammal, more preferably a human, may be carried out usingknown procedures, at dosages and for periods of time effective tomodulate breathing control and/or respiratory and ventilatory drive inthe patient. An effective amount of the therapeutic compound sufficientto achieve a therapeutic effect may vary according to factors, such asthe activity of the particular compound employed; the time ofadministration; the rate of excretion of the compound; the duration ofthe treatment; other drugs, compounds or materials used in combinationwith the compound; the state of the disease or disorder, age, sex,weight, condition, general health and prior medical history of thepatient being treated, and like factors well-known in the medical arts.Dosage regimens may be adjusted to provide the optimum therapeuticresponse. For example, several divided doses may be administered dailyor the dose may be proportionally reduced as indicated by the exigenciesof the therapeutic situation. A non-limiting example of an effectivedose range for a therapeutic compound s from about 0.01 mg/kg to 100mg/kg of body weight/per day. One of ordinary skill in the art would beable to study the relevant factors and make the determination regardingthe effective amount of the therapeutic compound without undueexperimentation.

The compositions comprising the cystine esters described herein may beadministered to an animal as frequently as several times daily, or itmay be administered less frequently, such as once a day, once a week,once every two weeks, once a month, or even less frequently, such asonce every several months or even once a year or less. It is understoodthat the amount of composition or cystine esters described herein dosedper day may be administered, in non-limiting examples, every day, everyother day, every 2 days, every 3 days, every 4 days, or every 5 days.For example, with every other day administration, a 5 mg per day dosemay be initiated on Monday with a first subsequent 5 mg per day doseadministered on Wednesday, a second subsequent 5 mg per day doseadministered on Friday, and so on. The frequency of the dose will bereadily apparent to the skilled artisan and will depend upon any numberof factors, such as, but not limited to, the type and severity of thedisease being treated, the type and age of the animal, etc.

Actual dosage levels of the active ingredients in the pharmaceuticalcompositions may be varied so as to obtain an amount of the activeingredient that is effective to achieve the desired therapeutic responsefor a particular patient, composition, and mode of administration,without being toxic to the patient.

A medical doctor, e.g., physician or veterinarian, having ordinary skillin the art may readily determine and prescribe the effective amount ofthe pharmaceutical composition required. For example, the physician orveterinarian could start doses of the compounds employed in thepharmaceutical composition at levels lower than that required in orderto achieve the desired therapeutic effect and gradually increase thedosage until the desired effect is achieved.

In particular embodiments, it is especially advantageous to formulatethe compound in dosage unit form for ease of administration anduniformity of dosage. Dosage unit form as used herein refers tophysically discrete units suited as unitary dosages for the patients tobe treated; each unit containing a predetermined quantity of therapeuticcompound calculated to produce the desired therapeutic effect inassociation with the required pharmaceutical vehicle. The dosage unitforms are dictated by and directly dependent on (a) the uniquecharacteristics of the therapeutic compound and the particulartherapeutic effect to be achieved, and (b) the limitations inherent inthe art of compounding/formulating such a therapeutic compound for thetreatment of breathing disorders in a patient.

In one embodiment, the compositions are administered to the patient indosages that range from one to five times per day or more. In anotherembodiment, the compositions are administered to the patient in range ofdosages that include, but are not limited to, once every day, every twodays, every three days to once a week, and once every two weeks. It willbe readily apparent to one skilled in the art that the frequency ofadministration of the various combination compositions will vary fromsubject to subject depending on many factors including, but not limitedto, age, disease or disorder to be treated, gender, overall health, andother factors.

Compounds for administration may be in the range of from about 1 μg toabout 7,500 mg, about 20 μg to about 7,000 mg, about 40 μg to about6,500 mg, about 80 μg to about 6,000 mg, about 100 μg to about 5,500 mg,about 200 μg to about 5,000 mg, about 400 μg to about 4,000 mg, about800 μg to about 3,000 mg, about 1 mg to about 2,500 mg, about 2 mg toabout 2,000 mg, about 5 mg to about 1,000 mg, about 10 mg to about 750mg, about 20 mg to about 600 mg, about 30 mg to about 500 mg, about 40mg to about 400 mg, about 50 mg to about 300 mg, about 60 mg to about250 mg, about 70 mg to about 200 mg, about 80 mg to about 150 mg, andany and all whole or partial increments there-in-between.

In some embodiments, the dose of a compound is from about 0.5 μg andabout 5,000 mg. In some embodiments, a dose of a compound used incompositions described herein is less than about 5,000 mg, or less thanabout 4,000 mg, or less than about 3,000 mg, or less than about 2,000mg, or less than about 1,000 mg, or less than about 800 mg, or less thanabout 600 mg, or less than about 500 mg, or less than about 200 mg, orless than about 50 mg. Similarly, in some embodiments, a dose of asecond compound as described herein is less than about 1,000 mg, or lessthan about 800 mg, or less than about 600 mg, or less than about 500 mg,or less than about 400 mg, or less than about 300 mg, or less than about200 mg, or less than about 100 mg, or less than about 50 mg, or lessthan about 40 mg, or less than about 30 mg, or less than about 25 mg, orless than about 20 mg, or less than about 15 mg, or less than about 10mg, or less than about 5 mg, or less than about 2 mg, or less than about1 mg, or less than about 0.5 mg, and any and all whole or partialincrements thereof.

Other embodiments described herein relate to a packaged pharmaceuticalcomposition comprising a container holding a therapeutically effectiveamount of a compound, alone or in combination with a secondpharmaceutical agent; and instructions for using the compound to treat,prevent, or reduce one or more symptoms of breathing disorder in apatient.

The term “container” includes any receptacle for holding thepharmaceutical composition or for managing stability or water uptake.For example, in one embodiment, the container is the packaging thatcontains the pharmaceutical composition, such as liquid (solution andsuspension), semisolid, lyophilized solid, solution and powder orlyophilized formulation present in dual chambers. In other embodiments,the container is not the packaging that contains the pharmaceuticalcomposition, i.e., the container is a receptacle, such as a box or vialthat contains the packaged pharmaceutical composition or unpackagedpharmaceutical composition and the instructions for use of thepharmaceutical composition. Moreover, packaging techniques are wellknown in the art. It should be understood that the instructions for useof the pharmaceutical composition may be contained on the packagingcontaining the pharmaceutical composition, and as such the instructionsform an increased functional relationship to the packaged product.However, it should be understood that the instructions may containinformation pertaining to the compound's ability to perform its intendedfunction, e.g., treating, preventing, or reducing a breathing disorderin a patient.

Routes of administration of any of the compositions includeinhalational, oral, nasal, rectal, parenteral, sublingual, transdermal,transmucosal (e.g., sublingual, lingual, (trans)buccal, (trans)urethral,vaginal (e.g., trans- and perivaginally), (intra)nasal, and(trans)rectal), intravesical, intrapulmonary, intraduodenal,intragastrical, intrathecal, epidural, intrapleural, intraperitoneal,subcutaneous, intramuscular, intradermal, intra-arterial, intravenous,intrabronchial, inhalation, and topical administration.

Compositions and dosage forms include, for example, tablets, capsules,caplets, pills, gel caps, troches, emulsions, dispersions, suspensions,solutions, syrups, granules, beads, transdermal patches, gels, powders,pellets, magmas, lozenges, creams, pastes, plasters, lotions, discs,suppositories, liquid sprays for nasal or oral administration, drypowder or aerosolized formulations for inhalation, compositions andformulations for intravesical administration and the like. It should beunderstood that the formulations and compositions are not limited to theparticular formulations and compositions that are described herein.

For oral application, particularly suitable are tablets, dragees,liquids, drops, capsules, caplets and gelcaps. Other formulationssuitable for oral administration include, but are not limited to, apowdered or granular formulation, an aqueous or oily suspension, anaqueous or oily solution, a paste, a gel, toothpaste, a mouthwash, acoating, an oral rinse, or an emulsion. The compositions intended fororal use may be prepared according to any method known in the art andsuch compositions may contain one or more agents selected from the groupconsisting of inert, non-toxic, generally recognized as safe (GRAS)pharmaceutically excipients which are suitable for the manufacture oftablets. Such excipients include, for example an inert diluent such aslactose; granulating and disintegrating agents such as cornstarch;binding agents such as starch; and lubricating agents such as magnesiumstearate.

Tablets may be non-coated or they may be coated using known methods toachieve delayed disintegration in the gastrointestinal tract of asubject, thereby providing sustained release and absorption of theactive ingredient. By way of example, a material such as glycerylmonostearate or glyceryl distearate may be used to coat tablets. Furtherby way of example, tablets may be coated using methods described in U.S.Pat. Nos. 4,256,108; 4,160,452; and 4,265,874 to form osmoticallycontrolled release tablets. Tablets may further comprise a sweeteningagent, a flavoring agent, a coloring agent, a preservative, or somecombination of these in order to provide for pharmaceutically elegantand palatable preparation. Hard capsules comprising the activeingredient may be made using a physiologically degradable composition,such as gelatin. The capsules comprise the active ingredient, and mayfurther comprise additional ingredients including, for example, an inertsolid diluent such as calcium carbonate, calcium phosphate, or kaolin.

Soft gelatin capsules comprising the active ingredient may be made usinga physiologically degradable composition, such as gelatin fromanimal-derived collagen or from a hypromellose, a modified form ofcellulose, and manufactured using optional mixtures of gelatin, waterand plasticizers such as sorbitol or glycerol. Such soft capsulescomprise the active ingredient, which may be mixed with water or an oilmedium such as peanut oil, liquid paraffin, or olive oil.

For oral administration, the compositions comprising the cystine estersdescribed herein may be in the form of tablets or capsules prepared byconventional means with pharmaceutically acceptable excipients, such asbinding agents; fillers; lubricants; disintegrates; or wetting agents.If desired, the tablets may be coated using suitable methods and coatingmaterials.

A tablet comprising the active ingredient may, for example, be made bycompressing or molding the active ingredient, optionally with one ormore additional ingredients. Compressed tablets may be prepared bycompressing, in a suitable device, the active ingredient in afree-flowing form, such as a powder or granular preparation, optionallymixed with one or more of a binder, a lubricant, an excipient, a surfaceactive agent, and a dispersing agent. Molded tablets may be made bymolding, in a suitable device, a mixture of the active ingredient, apharmaceutically acceptable carrier, and at least sufficient liquid tomoisten the mixture. Pharmaceutically acceptable excipients used in themanufacture of tablets include, but are not limited to, inert diluents,granulating and disintegrating agents, binding agents, and lubricatingagents. Known dispersing agents include, but are not limited to, potatostarch and sodium starch glycolate. Known surface-active agents include,but are not limited to, sodium lauryl sulphate. Known diluents include,but are not limited to, calcium carbonate, sodium carbonate, lactose,microcrystalline cellulose, calcium phosphate, calcium hydrogenphosphate, and sodium phosphate. Known granulating and disintegratingagents include, but are not limited to, corn starch and alginic acid.Known binding agents include, but are not limited to, gelatin, acacia,pre-gelatinized maize starch, polyvinylpyrrolidone, and hydroxypropylmethylcellulose. Known lubricating agents include, but are not limitedto, magnesium stearate, stearic acid, silica, and talc.

Granulating techniques are well known in the pharmaceutical art formodifying starting powders or other particulate materials of an activeingredient. The powders are typically mixed with a binder material intolarger permanent free-flowing agglomerates or granules referred to as a“granulation.” For example, solvent-using “wet” granulation processesare generally characterized in that the powders are combined with abinder material and moistened with water or an organic solvent underconditions resulting in the formation of a wet granulated mass fromwhich the solvent must then be evaporated.

Melt granulation generally consists in the use of materials that aresolid or semi-solid at room temperature (i.e., having a relatively lowsoftening or melting point range) to promote granulation of powdered orother materials, essentially in the absence of added water or otherliquid solvents. The low melting solids, when heated to a temperature inthe melting point range, liquefy to act as a binder or granulatingmedium. The liquefied solid spreads itself over the surface of powderedmaterials with which it is contacted, and on cooling, forms a solidgranulated mass in which the initial materials are bound together. Theresulting melt granulation may then be provided to a tablet press or beencapsulated for preparing the oral dosage form. Melt granulationimproves the dissolution rate and bioavailability of an active (i.e.,drug) by forming a solid dispersion or solid solution.

In some embodiments, the composition can be provided in the form of amulti-layer tablet comprising a layer providing for the delayed releaseof one or more compounds useful within the methods described herein, anda further layer providing for the immediate release of one or morecompounds useful within the methods. Using a wax/pH-sensitive polymermix, a gastric insoluble composition may be obtained in which the activeingredient is entrapped, ensuring its delayed release.

Liquid preparations for oral administration may be in the form ofsolutions, syrups or suspensions. The liquid preparations may beprepared by conventional means with pharmaceutically acceptableadditives such as suspending agents (e.g., sorbitol syrup, methylcellulose or hydrogenated edible fats); emulsifying agent (e.g.,lecithin or acacia); non-aqueous vehicles (e.g., almond oil, oily estersor ethyl alcohol); and preservatives (e.g., methyl or propylpara-hydroxy benzoates or sorbic acid). Liquid formulations of apharmaceutical composition, which are suitable for oral administrationmay be prepared, packaged, and sold either in liquid form or in the formof a dry product intended for reconstitution with water or anothersuitable vehicle prior to use.

Parenteral administration of a pharmaceutical composition includes anyroute of administration characterized by physical breaching of a tissueof a subject and administration of the pharmaceutical compositionthrough the breach in the tissue. Parenteral administration thusincludes, but is not limited to, administration of a pharmaceuticalcomposition by injection of the composition, by application of thecomposition through a surgical incision, by application of thecomposition through a tissue-penetrating non-surgical wound, and thelike. In particular, parenteral administration is contemplated toinclude, but is not limited to, subcutaneous, intravenous,intraperitoneal, intramuscular, intrasternal injection, and kidneydialytic infusion techniques.

Formulations of a pharmaceutical composition that can be used forparenteral administration comprise the active ingredient combined with apharmaceutically acceptable carrier, such as sterile water or sterileisotonic saline. Such formulations may be prepared, packaged, or sold ina form suitable for bolus administration or for continuousadministration. Injectable formulations may be prepared, packaged, orsold in unit dosage form, such as in ampules or in multidose containerscontaining a preservative. Injectable formulations may also be prepared,packaged, or sold in devices, such as patient-controlled analgesia (PCA)devices. Formulations for parenteral administration include, but are notlimited to, suspensions, solutions, emulsions in oily or aqueousvehicles, pastes, and implantable sustained-release or biodegradableformulations. Such formulations may further comprise one or moreadditional ingredients including, but not limited to, suspending,stabilizing, or dispersing agents. In one embodiment of a formulationfor parenteral administration, the active ingredient is provided in dry(i.e., powder or granular) form for reconstitution with a suitablevehicle (e.g., sterile pyrogen-free water) prior to parenteraladministration of the reconstituted composition.

The pharmaceutical compositions may be prepared, packaged, or sold inthe form of a sterile injectable aqueous or oily suspension or solution.This suspension or solution may be formulated according to the knownart, and may comprise, in addition to the active ingredient, additionalingredients such as the dispersing agents, wetting agents, or suspendingagents described herein. Such sterile injectable formulations may beprepared using a non-toxic parenterally acceptable diluent or solvent,such as water or 1,3-butanediol, for example. Other acceptable diluentsand solvents include, but are not limited to, Ringer's solution,isotonic sodium chloride solution, and fixed oils such as syntheticmono- or di-glycerides. Other parentally-administrable formulationswhich are useful include those which comprise the active ingredient inmicrocrystalline form in a recombinant human albumin, a fluidizedgelatin, in a liposomal preparation, or as a component of abiodegradable polymer system. Compositions for sustained release orimplantation may comprise pharmaceutically acceptable polymeric orhydrophobic materials such as an emulsion, an ion exchange resin, asparingly soluble polymer, or a sparingly soluble salt.

Formulations for topical administration include, but are not limited to,liquid or semi-liquid preparations, such as liniments, lotions,oil-in-water or water-in-oil emulsions such as creams, ointments orpastes, and solutions or suspensions. Topically administrableformulations may, for example, comprise from about 1% to about 10% (w/w)active ingredient, although the concentration of the active ingredientmay be as high as the solubility limit of the active ingredient in thesolvent. Formulations for topical administration may further compriseone or more of the additional ingredients described herein.

Enhancers of permeation may be used. These materials increase the rateof penetration of drugs across the skin. Typical enhancers in the artinclude ethanol, glycerol monolaurate, PGML (polyethylene glycolmonolaurate), dimethylsulfoxide, and the like. Other enhancers includeoleic acid, oleyl alcohol, ethoxydiglycol, laurocapram, alkanecarboxylicacids, dimethylsulfoxide, polar lipids, or N-methyl-2-pyrrolidone.

One acceptable vehicle for topical delivery of some of the compositionsof the invention may contain liposomes. The composition of the liposomesand their use are known in the art (i.e., U.S. Pat. No. 6,323,219).

In alternative embodiments, the topically active pharmaceuticalcomposition may be optionally combined with other ingredients, such asadjuvants, anti-oxidants, chelating agents, surfactants, foaming agents,wetting agents, emulsifying agents, viscosifiers, buffering agents,preservatives, and the like. In another embodiment, a permeation orpenetration enhancer is included in the composition and is effective inimproving the percutaneous penetration of the active ingredient into andthrough the stratum corneum with respect to a composition lacking thepermeation enhancer. Various permeation enhancers, including oleic acid,oleyl alcohol, ethoxydiglycol, laurocapram, alkanecarboxylic acids,dimethylsulfoxide, polar lipids, or N-methyl-2-pyrrolidone, are known tothose of skill in the art. In another aspect, the composition mayfurther comprise a hydrotropic agent, which functions to increasedisorder in the structure of the stratum corneum, and thus allowsincreased transport across the stratum corneum. Various hydrotropicagents such as isopropyl alcohol, propylene glycol, or sodium xylenesulfonate, are known to those of skill in the art.

The topically active pharmaceutical composition should be applied in anamount effective to affect desired changes. As used herein “amounteffective” shall mean an amount sufficient to cover the region of skinsurface where a change is desired. An active compound should be presentin the amount of from about 0.0001% to about 15% by weight volume of thecomposition. More preferable, it should be present in an amount fromabout 0.0005% to about 5% of the composition; most preferably, it shouldbe present in an amount of from about 0.001% to about 1% of thecomposition. Such compounds may be synthetically-or naturally derived.

A pharmaceutical composition may be prepared, packaged, or sold in aformulation for buccal administration. Such formulations may be in theform of tablets or lozenges made using conventional methods, and maycontain, for example, 0.1 to 20% (w/w) of the active ingredient, thebalance comprising an orally dissolvable or degradable composition and,optionally, one or more of the additional ingredients described herein.Alternately, formulations suitable for buccal administration maycomprise a powder or an aerosolized or atomized solution or suspensioncomprising the active ingredient. Such powdered, aerosolized, oraerosolized formulations, when dispersed, can have an average particleor droplet size in the range from about 0.1 to about 200 nanometers, andmay further comprise one or more of the additional ingredients describedherein. The examples of formulations described herein are not exhaustiveand it is understood that the invention includes additionalmodifications of these and other formulations not described herein, butwhich are known to those skilled in the art.

In one embodiment, the composition is designed to promote controlledrelease of the drug, such that the location, extent and rate of exposureof the compound when administered are modulated. Factors that affect thetarget zone for exposure of an orally administered drug may be thedrug's pH and enzymatic stability, reactivity with other drugs (e.g.,certain antibiotics), solubility as a salt or free base, ionizationbehavior, and pharmacodynamic and pharmacokinetic behaviors in specificenvironments.

Controlled- or sustained-release formulations of a pharmaceuticalcomposition may be made using conventional technology. In some cases,the dosage forms to be used can be provided as slow orcontrolled-release of one or more active ingredients therein using, forexample, hydropropylmethyl cellulose, other polymer matrices, gels,permeable membranes, osmotic systems, multilayer coatings,microparticles, liposomes, or microspheres or a combination thereof toprovide the desired release profile in varying proportions.

Controlled-release of an active ingredient can be stimulated by variousinducers, for example water, pH, temperature, enzymes, bacteria, orother physiological conditions or compounds.

In certain embodiments, the formulations of described herein may be, butare not limited to, short-term, rapid-offset, as well as controlled, forexample, sustained release, delayed release and pulsatile releaseformulations. The active drug substance can also be coated on animplantable medical device to be eluted or be released using a remotelyactivated system.

The term sustained release is used in its conventional sense to refer toa drug formulation that provides for gradual release of a drug over anextended period of time, and that may, although not necessarily, resultin substantially constant blood levels of a drug over an extended timeperiod. The period of time may be as long as a month or more and shouldbe a release that is longer that the same amount of agent administeredin bolus form.

For sustained release, the compounds may be formulated with a suitablepolymer or hydrophobic material which provides sustained releaseproperties to the compounds. As such, the compounds for use the methodof the invention may be administered in the form of microparticles, forexample, by injection or in the form of wafers or discs by implantation(drug embedded in polymeric matrices).

In some embodiments, the compounds described herein are administered toa patient, alone or in combination with another pharmaceutical agent,using a sustained release formulation.

The term delayed release is used herein in its conventional sense torefer to a drug formulation that provides for an initial release of thedrug after some delay following drug administration and that may,although not necessarily, includes a delay of from about 10 minutes upto about 24 hours.

The term pulsatile release is used herein in its conventional sense torefer to a drug formulation that provides release of the drug in such away as to produce pulsed plasma profiles of the drug after drugadministration.

The term immediate release is used in its conventional sense to refer toa drug formulation that provides for release of the drug immediatelyafter drug administration.

As used herein, short-term refers to any period of time up to andincluding about 24 hours, about 12 hours, about 8 hours, about 7 hours,about 6 hours, about 5 hours, about 4 hours, about 3 hours, about 2hours, about 1 hour, about 40 minutes, about 20 minutes, or about 10minutes and any or all whole or partial increments thereof after drugadministration after drug administration.

As used herein, rapid-offset refers to any period of time up to andincluding about 24 hours, about 12 hours, about 8 hours, about 7 hours,about 6 hours, about 5 hours, about 4 hours, about 3 hours, about 2hours, about 1 hour, about 40 minutes, about 20 minutes, or about 10minutes, and any and all whole or partial increments thereof after drugadministration.

In some embodiments, compounds described herein are formulated with anenteric coating, which has been modified by adding plasticizers to thepolymer before coating. The plasticizers may be added to adjustresistance to chipping or cracking of the coating, while also loweringthe glass transition temperature of the coating to enable smoothness andeven spreadability of the coating during its application. Suitableplasticizers include polyethylene glycol 8000 (PEG 8000), triethylcitrate (TEC), and triacetin, which may be incorporated into thepolymeric enteric coating agent.

Compounds described herein may be enterically formulated under a varietyof dosage forms, including (but not limited to) capsules, granules ofthe active drug itself, beads, micro spheres, and tablets. In oneembodiment, the composition comprises a drug encapsulated in a capsuleenterically coated to release the drug in the duodenum or otherintestinal environment. In another embodiment, pharmaceuticallyacceptable capsules include hard capsules. In yet another embodiment,pharmaceutically acceptable capsules include soft gelatin capsules.

In some embodiments, a composition comprising the cystine estersdescribed herein is encapsulated in pure granular or powdered form, withno carriers, excipients or other pharmaceutically acceptable additives.In another embodiment, a compound described herein is encapsulatedtogether with one or more pharmaceutically acceptable carriers,excipients, antioxidants, antifungals, (e.g., benzoic and ascorbic acidsand their salts, and phenolic compounds such as methyl, ethyl, propyland butyl p-hydroxybenzoate (parabens)), antimicrobial preservatives,colorants, and flavorants. The excipients may aid in capsule-fillingbehavior, stability, and in the distribution of the drug when thecapsule disintegrates in the body. In another embodiment, granulesand/or powders of a compound are enterically coated before being placedin a capsule. The enterically coated granules and/or powders placed inthe capsule may feature one or several types of enteric coating toenable delivery of the drug to different regions of the intestine. Thecapsule may lack enteric coating or may be coated with an entericcoating that is the same as or distinct from the coating applied to anyof the enterically coated materials inside the capsule.

In one embodiment, a composition comprising the cystine esters describedherein is encapsulated in a liquid in the form of a solution orsuspension in water or various pharmaceutically acceptable oils or otherdispersion medium, optionally with such excipients as cosolvents (e.g.,PEG 300, PEG 400, propylene glycol, glycerol, tween 80, ethanol),solubility enhancers (e.g., sorbitol, dextrose), wetting agents (e.g.,thickening agents), buffers (e.g., disodium hydrogen phosphate),antioxidants, antifungals, preservatives, colorants and flavorants. Inone embodiment, a composition comprising the cystine esters describedherein is formulated for liquid filled capsules in the form of the puredrug as granules and/or powders in the liquid. In another embodiment,the capsule containing the composition in liquid is enterically coated.In yet another embodiment, granules and/or powders of a compound areenterically coated before being placed in a liquid and the combinationplaced in a capsule. The enterically coated granules and/or powder mayfeature one or several types of enteric coating to enable delivery ofthe drug to distinct regions of the intestine. The capsule may lackenteric coating or may be coated with an enteric coating that is thesame as or distinct from the coating applied to any of the entericallycoated materials inside the capsule.

In one embodiment, a composition comprising the cystine esters describedherein is encapsulated in a capsule comprised of material that affordspost-gastric drug delivery without the need for the separate applicationof an enteric coating (e.g., Entericare enteric softgels). Thecomposition may be encapsulated in such capsules as granules or powderswith or without excipients, and as solutions or suspensions as describedabove.

In one embodiment, the solid particles of a compound, as a variety ofparticle sizes and particle size distributions, are admixed withexcipients, such as microcrystalline cellulose or lactose and formed asa bead that comprises the drug-containing core onto which the entericcoating is applied. In another embodiment, a compound is formed as asuspension or solution including, optionally, buffers (e.g., aq. 1 N HClwith tris(hydroxymethyl)aminomethane “TRIS”), and binders (e.g., OpadryClear Coat Powder) and coated onto a base particle, for example sugarbeads (e.g., Sugar Spheres, NF particles) to form a bead. In yet anotherembodiment, the beads are enterically coated. In yet another embodiment,a compound is formulated as enterically coated beads, as describedabove, and the beads further formulated by encapsulation. In yet anotherembodiment, a combination of beads with different types of entericcoating is encapsulated, such that once released from the capsule, thecompound is made available in a controlled manner at different regionsranging from the duodenum to other parts of the intestine. The capsulemay lack enteric coating or may be coated with an enteric coating thatis the same as or distinct from the coating applied to any of theenterically coated materials inside the capsule.

In one embodiment, a composition comprising the cystine esters describedherein is formulated as tablets or caplets which alone or in combinationwith other formulation components deliver drug to the duodenum or otherintestinal region. In another embodiment, a composition comprising thecystine esters described herein is formulated as tablets or caplets thatare enterically coated and that constitute the dosage form administered.In yet another embodiment, tablets or caplets of suitable size and shapeare placed inside a capsule. In yet another embodiment, the capsule isenterically coated and contains non-enterically coated tablets orcaplets, which are released from the capsule in the duodenum or otherintestinal region. In yet another embodiment, the capsule is designed todisintegrate in the stomach and release enterically coated tablets orcaplets for subsequent delivery to duodenum or other intestinal regions.In yet another embodiment, the capsule and tablets or caplets containedwithin are both enterically coated to provide further control over therelease of the tablets or caplets from the capsule, and the subsequentrelease of the drug from the tablet or caplet. In yet anotherembodiment, tablets or caplets featuring a variety of enteric coatingare combined and placed in a capsule which itself may optionally beenterically coated as well. Materials useful for enteric coatings fortablets and caplets include but are not limited to those described abovefor application to capsules.

Enteric coatings may permit premature drug release in acidic media. Inone embodiment, a compound of the present invention is formulated suchthat a subcoating is applied before the enteric coating is applied. Thesubcoating may comprise application to the enteric substrate of asoluble subcoating agent, examples of which arehydroxypropylmethylcellulose, povidone, hydroxypropyl cellulose,polyethylene glycol 3350, 4500, 8000, methyl cellulose, pseudoethylcellulose and amylopectin. It is understood that similar type ofsynthetic and semisynthetic polymeric products from other companies maybe used. A thin subcoating layer on the enteric substrate impedes waterpenetration through the enteric coating on the capsule shell or into thecore where the active ingredient is located, preventing premature drugrelease. The subcoating may also promote the release of the drug in abasic environment by moderating the acidic microenvironment at theinterface between the core and the enteric coating. In one embodiment, acompound is formulated with a subcoating containing organic acidsintended to promote more rapid polymer dissolution of a capsule as thecoating degrades in environments with pH 5-6, promoting a rapid releaseof the drug in basic media.

Other embodiments described herein relate to a method of treating asubject in need thereof, such as a subject without normal ventilationand/or normal breathing control, by administering the compositionscomprising the cystine esters described herein, and additionallytreating the patient using a device to support breathing. Such devicesinclude, but are not limited to, ventilation devices, CPAP and BiPAPdevices.

Mechanical ventilation is a method to mechanically assist or replacespontaneous breathing. Mechanical ventilation is typically used after aninvasive intubation, a procedure wherein an endotracheal or tracheostomytube is inserted into the airway. It is normally used in acute settings,such as in the ICU, for a short period of time during a serious illness.It may also be used at home or in a nursing or rehabilitationinstitution, if patients have chronic illnesses that require long-termventilation assistance. The main form of mechanical ventilation ispositive pressure ventilation, which works by increasing the pressure inthe patient's airway and thus forcing air into the lungs. Less commontoday are negative pressure ventilators (for example, the “iron lung”)that create a negative pressure environment around the patient's chest,thus sucking air into the lungs. Types of mechanical ventilation are:conventional positive pressure ventilation, high frequency ventilation,non-invasive ventilation (non-invasive positive pressure ventilation orNIPPY), proportional assist ventilation (PAY), adaptive servoventilation (ASV) and neurally adjusted ventilatory assist (NAVA).

Non-invasive ventilation refers to all modalities that assistventilation without the use of an endotracheal tube. Non-invasiveventilation is primarily aimed at minimizing patient discomfort and thecomplications associated with invasive ventilation, and is often used incardiac disease, exacerbations of chronic pulmonary disease, sleepapnea, and neuromuscular diseases. Non-invasive ventilation refers onlyto the patient interface and not the mode of ventilation used; modes mayinclude spontaneous or control modes and may be either pressure orvolume cycled modes.

Some commonly used modes of NIPPY include continuous positive airwaypressure (CPAP). This kind of machine has been used mainly by patientsfor the treatment of sleep apnea at home, but now is in widespread useacross intensive care units as a form of ventilatory support. The CPAPmachine stops upper airway obstruction by delivering a stream ofcompressed air via a hose to a nasal pillow, nose mask or full-facemask, splinting the airway open (keeping it open under air pressure) sothat unobstructed breathing becomes possible, reducing and/or preventingapneas and hypopneas. When the machine is turned on, but prior to themask being placed on the head, a flow of air comes through the mask.After the mask is placed on the head, it is sealed to the face and theair stops flowing. At this point, it is only the air pressure thataccomplishes the desired result. This has the additional benefit ofreducing or eliminating the extremely loud snoring that sometimesaccompanies sleep apnea.

Bi-level positive airway pressure (BIPAP) alternate between inspiratorypositive airway pressure (IPAP) and a lower expiratory positive airwaypressure (EPAP), triggered by patient effort. On many such devices,backup rates may be set, which deliver IPAP pressures even if patientsfail to initiate a breath.

The invention is further illustrated by the following example, which isnot intended to limit the scope of the claims.

EXAMPLE

We evaluated a novel class of thiol-based respiratory stimulants. Theoriginal compounds made use of the findings that erythrocytic hemoglobintransports not only CO₂ and O₂, but also thiol-bound nitric oxide (NO),and that erythrocytic thiol-bound NO content decays logarithmically as afunction of changes in oxyhemoglobin saturation. Thiol-containingcompounds, such as glutathione or N-acetylcysteine (NAC) accelerate lossof NO from deoxyhemoglobin and can serve as potent respiratorystimulants, increasing minute ventilation in humans and animals.N-acetylcysteine signals erythrocytic hemoglobin desaturation andaugments hypoxia-induced increases minute ventilation. Relative toplacebo, humans receiving oral NAC three times daily had a three-foldgreater increase in minute ventilation (24±4% versus 8±3%) when exposedacutely to isocapnic hypoxia. However, high NAC doses were required. Westudied the details of this pathway worked out in both rat andtransgenic mouse models.

To target this pathway, we screened thiol-containing compounds asrespiratory stimulants. We discovered several that were more potent thanNAC. Of these, the compounds with the most sustained activity wereD-Cystine dimethylester (D-Cystine diME) and D-Cystine diethylester(D-Cystine diEE). We found that oxidized thiols such as D-Cystine diMEand D-Cystine diEE may be longer-acting than the corresponding reducedthiols—such as D-Cysteine ethyl ester (D-CYSee)—because they are morestable, with gradual reduction to the active, but shorter-acting,reduced form in vivo; this reduction has previously been demonstrated.The D-isomer may be more active than the corresponding L-isomer becauseof slower metabolism to intracellular cellular cysteine-containingpeptides and proteins—permitting sustained activity. This was thestarting premise, but our more recent work suggests additionally thatD-Cystine diME may inhibit a specific potassium channel involved inrespiratory control. We also found that modifications of the cysteinemolecule, including simple N-acetylation, decrease activity. Thesecompounds can be used as a novel treatment option for COPD and otherpulmonary patients with acute respiratory depression. The principaltarget population can include patients with impaired ventilatory and/orrespiratory drive who are at risk for requiring mechanical ventilationbecause of either an acute exacerbation of underlying lung disease or anacute requirement for narcotic analgesia.

D-Cystine diME Given Parenterally Causes a Sustained Increase in TidalVolume and Respiratory Frequency in Conscious RatsD-Cystine diME Increases Minute Ventilation in Conscious Rats

Plethysmographic measurements in conscious male adult Sprague-Dawleyrats revealed that D-Cystine diME (500 μmol/kg, i.v.) elicited robustincreases in frequency of breathing, tidal volume and minute ventilationof 20 min in duration (FIG. 1). Identical injections of D-CYSee(D-Cysteine ethyl ester) and L-CYSee (L-Cysteine ethyl ester) hadsimilar effects, but D-Cystine diME provided the most sustained effect.We hypothesize that oxidized D-cystine esters have sustained activitybecause they are taken up into neuroregulatory cells and erythrocytes,slowly reduced to D-cysteine, but are not inactivated by incorporationinto peptides and proteins by enzymes that recognize L-cysteine.

D-Cystine diME is the Most Active Member of this Novel Class ofRespiratory Stimulants

The total responses recorded over the 30 min post-injection period (%baseline) are summarized in FIG. 2. These data providestructure-activity relationship information. Injection of the vehicle(saline) elicited minor effects. L-serine ethyl ester (L-SERee), wasminimally active, demonstrating the key importance of the sulfur atom inthese responses. The comparatively minor effects of L-N-acetylcysteinemethylester (L-NACme) demonstrate that placing acetyl moiety on thenitrogen atom of L-cysteine also impairs efficacy. Of key importancewere the findings that (1) L-cysteine methylester (L-CYSme) was asefficacious as L-CYSee (L-Cysteine ethyl ester), (2) D-CYSee (D-Cysteineethyle ester) was more efficacious that L-CYSee/L-CYSme, and (3)D-Cystine diME was the most efficacious of the test compounds.

Dose-Response Effects of D-Cystine diME in Conscious Rats

A key feature of therapeutic drug is dose-dependency. As shown in FIG.3, the ventilatory responses elicited by D-CYS diME clearlydose-dependent.

D-Cystine diME also Elicits Pronounced Ventilatory Responses inConscious Mice

In order to assess whether the responses to D-Cystine diME were uniqueto rats, we examined the effects of a 250 μmol/kg dose of D-Cystine diMEon ventilatory parameters in conscious (adult male) C57 black 6 (C57BL6)mice. As seen in FIG. 4, this dose of D-Cystine diME elicited robustincreases in frequency of breathing, tidal volume and minute ventilationof approximately 20 min in duration. The responses were equivalent tothose in conscious rats.

D-Cystine diEE and D-Cystine diME Reverse Opioid-Induced RespiratoryDepression in Conscious Rats

D-Cystine diEE Elicits an Immediate and Sustained Reversal of theVentilatory Depressant Effects of Morphine

As shown in FIG. 5, a bolus injection of D-Cystine diEE (500 μmol/kg,i.v.) elicited an immediate and sustained reversal of the ventilatorydepressant effects of morphine (10 mg/kg, i.v.) including the derivedparameter, tidal volume/inspiratory time (Vt/Ti), which is an index ofcentral respiratory drive. The dramatic and sustained effect ofD-Cystine diEE on tidal volume is a vital effect because the decrease intidal volume is an integral component of morphine-induced changes inarterial blood-gas (ABG) chemistry (see below).

D-Cystine diME Reverses Morphine's Effects on ABG Chemistry

As shown in FIG. 6, the bolus injection of D-Cystine diME (500 μmol/kg,i.v.) reversed the deleterious actions of morphine (10 mg/kg, i.v.) onABG chemistry and Alveolar-arterial (A-a) gradient (index ofgas-exchange in the lungs). The bolus injection of D-cystine itself (500μmol/kg, i.v.) elicited minor delayed effects (FIG. 6).

D-CYSee Reverses the Ventilatory Depressant Effects of Morphine

As shown in FIG. 7, the possibility that D-cystine diME exerts itseffects via generation of D-Cysteine in cells is supported by findingsthat injections of D-CYSee (2×500 μmol/kg, i.v.) also elicited asustained reversal of the effects of morphine (10 mg/kg, i.v.). As withD-Cystine diME, a key feature of D-CYSee is its ability to reverse theeffects of morphine on tidal volume.

D-CYSee Reverses Morphine's Effects on ABG Chemistry and A-a Gradient

As seen in FIG. 8, a single injection of D-CYSee (500 μmol/kg, i.v.)elicited a sustained reversal of the deleterious effects of morphine (10mg/kg, i.v.) on ABG chemistry and A-a gradient. D-cysteine itself (500μmol/kg, i.v.) elicited minimal effects.

Prior Infusion of L-CYSee Blunts the Ventilatory Depressant Effects ofMorphine

Although the ability of bolus injections of D-Cystine diME and D-CYSeeto reverse opioid-induced depression of ventilation is of vitalimportance, it is also important to determine whether prioradministration of these compounds can prevent the deleterious actions ofopioids. Although we are yet to examine the D-isomers, we haveestablished that prior infusion of L-CYSee (14.3 μmol/kg/min, total doseof 500 μmol/kg, i.v.) over 35 min (1) dramatically increased peakinspiratory flow and respiratory drive (Vt/Ti) in conscious rats, and(2) markedly blunted the subsequent effects of a bolus injection ofmorphine (10 mg/kg, i.v.). As can be seen, a subsequent injection ofL-CYSee (250 μmol/kg/min) elicited prompt beneficial effects in theserats (FIG. 9).

Prior Infusion of L-CYSee but Not L-SERee Blunts Morphine's Effects onABG Chemistry and A-a Gradient

As seen in FIG. 10, the prior infusion of L-CYSee 14.3 μmol/kg/min,total dose of 500 μmol/kg, i.v. over 35 min) virtually eliminated thedeleterious effects of morphine (10 mg/kg, i.v.) on ABG chemistry andA-a gradient. In contrast, the infusion of identical amount of L-SEReewas without effect on morphine, again high-lighting the key involvementof the sulfur atom in the beneficial effects of L-CYSee.

Preliminary Toxicology Studies Hemodynamics

L-CYSee (500 μmol/kg, i.v.) elicited substantial transient decreases inmean arterial blood pressure (MAP) via decreases in cardiac output andheart rate (no changes in total peripheral resistance). In contrast,L-CYSee, and in particular D-Cystine diME, elicited minimal responses(FIG. 11).

Analgesia

Although pretreatment with D-CYSee (500 μmol/kg, i.v.) did not affectthe initial level of analgesia (paw withdrawal latency) elicited bymorphine (5 mg/kg, i.v.) in conscious rats, the analgesia decayed morequickly (FIG. 12). D-cystine diethyl ester (D-cystine DEE) (500 μmol/kg,i.v.) however does not attenuate morphine analgesia elicited by 10 mg/kgof morphine (dose eliciting depression of breathing in our ventilatorystudies) (FIG. 13), suggesting it may be an ideal respiratory stimulantin the setting of narcotic-induced respiratory depression.

From the above description of the invention, those skilled in the artwill perceive improvements, changes and modifications. Suchimprovements, changes and modifications within the skill of the art areintended to be covered by the appended claims. All references,publications, and patents cited in the present application are hereinincorporated by reference in their entirety.

1. A method of stimulating ventilatory and/or respiratory drive in asubject in need thereof, the method comprising: administering to thesubject a therapeutically effective amount of a composition comprising acystine ester or a pharmaceutically acceptable salt thereof.
 2. Themethod of claim 1, wherein the therapeutically effective amount is anamount effective to stimulate the ventilatory and/or respiratory driveof the subject.
 3. The method of claim 1, wherein the cystine ester hasthe formula:

where R¹ and R² are the same or different and are selected from thegroup consisting of H, unsubstituted or substituted C₁-C₂₄ alkyl, C₂-C₂₄alkenyl, C₂-C₂₄ alkynyl, C₃-C₂₀ aryl, heterocycloalkenyl containing from5-6 ring atoms, heteroaryl, and heterocyclyl containing from 5-14 ringatoms, wherein at least one of R¹ and R² is not a H; or pharmaceuticallyacceptable salts thereof.
 4. The method of claim 3, wherein R¹ and R²are independently H or an unsubstituted or substituted C₁-C₂₄ alkyl,wherein at least one of R¹ and R² is not a H.
 5. The method of claim 3,wherein R¹ and R² are independently selected from the group consistingof H, methyl, ethyl, propyl, and butyl, wherein at least one of R¹ andR² is not a H.
 6. The method of claim 1, wherein the cystine ester is acystine dialkyl ester.
 7. The method of claim 6, wherein the cystinedialkyl ester is a D-cystine dialkyl ester or pharmaceuticallyacceptable salt thereof.
 8. The method of claim 6, wherein the cystinedialkyl ester is selected from the group consisting of cystine dimethylester, cystine diethyl ester, combinations thereof, and pharmaceuticallyacceptable salts thereof.
 9. The method of claim 6 wherein the cystinedialkyl ester is D-cystine dimethyl ester.
 10. The method of claim 1,wherein the subject has or is at increased risk of respiratorydepression, sleep apnea, apnea of prematurity, obesity-hypoventilationsyndrome, primary alveolar hypoventilation syndrome, dyspnea, altitudesickness, hypoxia, hypercapnia, cystic fibrosis, and chronic obstructivepulmonary disease (COPD).
 11. The method of claim 1, wherein the subjecthas or is at increase risk of respiratory depression, wherein therespiratory depression is caused by anesthetic, a sedative, anxiolyticagent, a hypnotic agent, alcohol, and/or a narcotic.
 12. The method ofclaim 1, further comprising administering at least one additionalcomposition selected from the group consisting of doxapram andenantiomers thereof, acetazolamide, almitrine, theophylline, caffeine,methylprogesterone and related compounds, sedatives that decreasearousal threshold in sleep disordered breathing patients, sodiumoxybate, benzodiazepine receptor agonists, orexin antagonists, tricyclicantidepressants, serotonergic modulators, adenosine and adenosinereceptor and nucleoside transporter modulators, cannabinoids, orexins,melatonin agonists, ampakines, and combinations thereof.
 13. The methodof claim 1, wherein the composition is administered to the subjectsystemically.
 14. A method of treating a breathing disorder in a subjectin need thereof, the method comprising: administering to the subject atherapeutically effective amount of a composition comprising a cystineester or a pharmaceutically acceptable salt thereof.
 15. The method ofclaim 14, wherein the therapeutically effective amount is an amounteffective to stimulate the ventilatory and/or respiratory drive of thesubject.
 16. The method of claim 14, wherein the cystine ester has theformula:

wherein R¹ and R² are the same or different and are selected from thegroup consisting of H, unsubstituted or substituted C₁-C₂₄ alkyl, C₂-C₂₄alkenyl, C₂-C₂₄ alkynyl, C₃-C₂₀ aryl, heterocycloalkenyl containing from5-6 ring atoms, heteroaryl, and heterocyclyl containing from 5-14 ringatoms, wherein at least one of R¹ and R² is not a H; or pharmaceuticallyacceptable salts thereof.
 17. The method of claim 16, wherein R¹ and R²are independently H or a unsubstituted or substituted C₁-C₂₄ alkyl,wherein at least one of R¹ and R² is not a H.
 18. The method of claim16, wherein R¹ and R² are independently selected from the groupconsisting of H, methyl, ethyl, propyl, and butyl, wherein at least oneof R¹ and R² is not a H.
 19. The method of claim 16, wherein the cystineester is a cystine dialkyl ester.
 20. The method of claim 19, whereinthe cystine dialkyl ester is a D-cystine dialkyl ester orpharmaceutically acceptable salt thereof.
 21. The method of claim 19,wherein the cystine dialkyl ester is selected from the group consistingof cystine dimethyl ester, cystine diethyl ester, combinations thereof,and pharmaceutically acceptable salts thereof.
 22. The method of claim19, wherein the cystine dialkyl ester is D-cystine dimethyl ester. 23.The method of claim 14, the breathing disorder is or associated withrespiratory depression, sleep apnea, apnea of prematurity,obesity-hypoventilation syndrome, primary alveolar hypoventilationsyndrome, dyspnea, altitude sickness, hypoxia, hypercapnia, cysticfibrosis, and/or chronic obstructive pulmonary disease (COPD).
 24. Themethod of claim 14, wherein the breathing disorder is respiratorydepression, wherein the respiratory depression is caused by anesthetic,a sedative, anxiolytic agent, a hypnotic agent, alcohol, and/or anarcotic.
 25. The method of claim 14, further comprising administeringat least one additional composition selected from the group consistingof doxapram and enantiomers thereof, acetazolamide, almitrine,theophylline, caffeine, methylprogesterone and related compounds,sedatives that decrease arousal threshold in sleep disordered breathingpatients, sodium oxybate, benzodiazepine receptor agonists, orexinantagonists, tricyclic antidepressants, serotonergic modulators,adenosine and adenosine receptor and nucleoside transporter modulators,cannabinoids, orexins, melatonin agonists, ampakines, and combinationsthereof.
 26. The method of claim 14, wherein the composition isadministered to the subject systemically. 27-34. (canceled)